The focus of my work – including this substack, is on transforming the physical environment. I often say, my overarching goal in life is to create a more beautiful world. It’s not easy. There is a lot one must do to change the world around us. The real world is political. It's expensive. Gravity exists. But I find it to be worth it. And yet, I often wonder why it is so challenging. There are many reasons for this, but one that I am realizing is increasingly impactful, even though I feel like I've known intuitively for a long time is this.

We live in two worlds.

For me, and others of my millennial generation, the physical world was the one we were born into. But the digital world is the one we grew up in. We are the bridge generation—caught between Baby Boomers, who mastered physical spaces but struggle with digital ones, and Gen Z, who navigate digital realms effortlessly while sometimes feeling lost in physical spaces.

The Internet and its infinite offshoot products emerged as tools to connect us across geography and then evolved into a whole new ecosystem. While not openly at odds, our two worlds, physical and digital, are in cold competition for resources, attention, and significance. Every time we scroll instead of stroll, stream instead of attend, or Zoom instead of show up, we choose one world over the other. Every dollar invested in digital places is one less invested in the physical places.

It's time to acknowledge that energy toward transforming the physical environment is in competition with a focus from governments, organizations, and consumers on the digital environment. Both are made up of actors inhabiting spaces, but it's important to understand the similarities and differences in the rules that govern how these different spaces are formed. This matters for anyone working to improve the physical world – politicians, architects, urban designers, community groups, and everyday citizens.

And right now, the digital world is winning the competition for our focus. What we're experiencing goes beyond a gradual shift—it’s a fundamental transformation of how humans relate to space itself.

Why Digital is Ahead

The digital world offers what the physical world cannot in our high-friction, high-inflation, high-competition reality:

1. Frictionless expansion: No permits, no construction delays, no physical constraints

2. New frontier opportunities: Unclaimed territory where newcomers can still stake ground. The 21st centuryWest.

3. Immediate feedback: Build, test, fail, rebuild in hours or days, not years. Agency is at your fingertips

4. Exponential rather than linear growth: Digital products can reach millions without physical manufacturing

5. Controlled interaction environments: You choose who you interact with in spaces that are broadly safer and cleaner than their physical counterparts

6. Upward mobility: The ability to improve our lives with far more individual freedom than the physical world offers. The digital world offers the opportunity for self-reinvention that can feel impossible in a physical world bogged down by various modern caste systems.

7. Infinite density: As population increases, the area needed to accommodate it remains constant - 0

In the physical world, making change requires permission. In the digital, act first and then ask for forgiveness.

A decade ago, Peter Thiel observed that we lived in a world where "bits were unregulated and atoms were regulated." This division has only deepened, creating compounding effects as the physical environment grows increasingly burdened by friction while the digital world remains nearly frictionless.

A Typological Inventory of Physical and Digital Place

With the advent of digital places, it's helpful to catalog and compare the types of spaces in both worlds. Interestingly, both physical and digital realms contain similar categories of space. They serve the same fundamental human functions – connect, gather, compete, and trade.

Infrastructure (connect)

Physical: Roads, airports, train stations, utility grids, urban grids
Digital: Social platforms, email, cloud networks, search engines

Physical infrastructure moves objects through space. Digital infrastructure moves data across networks.

The physical version is constrained by geography, materials, and physics. Building a highway requires land acquisition, environmental impact studies, materials, machinery, and years of construction. The digital version scales to billions of users overnight with negligible marginal cost.

Physical infrastructure deteriorates over time, requiring constant maintenance. Fixing something usually means shutting down a place to conduct work on it. Digital infrastructure decays too, but its obsolescence doesn't become blight. If a website goes offline and no one is there to notice, does it make a difference? Digital infrastructure can be updated instantly, globally, and often invisibly to users.

What's startling is how much we've come to rely on digital infrastructure over physical infrastructure. The A train being rerouted feels inconvenient. Instagram going down feels like the apocalypse. And now when digital infrastructure fails, the physical world grinds to a halt—as we saw with the July 2024 CrowdStrike outage that paralyzed global airports, grounded thousands of flights, and affected everything from hospitals to banks.

Commons (gather)

Physical: Parks, cafés, libraries, plazas
Digital: Discord servers, WhatsApp groups, Clubhouse rooms, multiplayer games, Substack

We are social animals drawn to third spaces for mingling and connection. Physical commons still attract us, but they come with friction – they're hard to get to, too expensive, too noisy, or too crowded.

The digital world, by contrast, can accommodate unnatural density. Spaces can scale from a few people to thousands through connectivity. We can share experiences and live vicariously through others, traveling to far-off locations in the real world with the swipe of a thumb.

Even approaching strangers has changed. The spontaneous connections that once defined urban life have been outsourced to apps and platforms, making our physical spaces more inert. As this shift continues, we're witnessing a profound alteration in the DNA of our communities and how we form connections within them.

Arenas (compete)

Physical: Courts, stadiums, debate halls, protest grounds
Digital: Twitter threads, Reddit forums, Twitch streams, online gambling, podcasts

Humans need space to compete. We need to be able to see where ideas diverge and which ones can emerge. We are inspired by victory and resilience.

The digital world is where ideas are largely contested now. The physical world is still where we witness sport, but it is being consumed ever more rapidly on digital platforms. I can’t remember when I last witnessed a real, live debate, but there’s always someone arguing in the comment section.

Physical competition comes with natural constraints that test the limits of the human body. The arena itself has boundaries, creating scarcity that adds value for those present. Proximity matters – being courtside at a championship game provides an experience that can't be replicated on television. The physical presence of opponents and spectators adds weight to the competition itself.

Digital competition removes these boundaries to focus on the limits of human thought. The always-on nature of these spaces leads to argument fatigue. Algorithms amplify the most divisive voices, while the absence of human cues enables a toxicity few would display face-to-face.

Markets (trade)

Physical: Stores, malls, restaurants, service providers
Digital: Amazon, UberEats, Tinder

Physical markets have operating hours. They close sometimes. People working there go home to sleep. Digital markets run 24/7 (except B&H's website on Saturdays – charming, if not sometimes minorly frustrating counterpoint to some traditions surviving across worlds).

The internet's growth accelerated dramatically when it became a way to sell things. Digital real estate on social media platforms is now as valuable as its ability to sell to the user.

The most profound and impactful shift might be in the mating market. Dating apps have largely replaced chance meetings. The mating dance has moved from bars and bookstores to swiping sessions on couches. When people are less inclined to venture out into the physical world to find a partner, we've eliminated the orginial reason for human collectivity and the spaces that support it. The consequences of digital alternatives to in-person sexual experiences are profound, not just for society but for human development itself.

Time and Space

Perhaps the starkest distinction between the two worlds is the role that time plays in each one.

The physical world enables permanence. We cherish thousand-year-old cathedrals and million-year-old mountains. We admire buildings that have withstood generations. The physical realm accumulates meaning through endurance.

The digital world valorizes novelty. Obsolescence is a constant possibility in a world optimizing for faster, newer, and more engrossing experiences. Moore's Law reminds us that the next technological advancement is just a few months away. Trends rise and dissolve within days (how much can we Ghibli?). The digital realm celebrates speed and reinvention.

The digital world also encourages experimentation. The lack of friction means you can try, fail, and try again with minimal consequences. You can't Ctrl+Z the physical world.

The Great Inversion

After the pandemic, I’ve noticed a strange reversal. Physical spaces now compete for relevance by proving their digital worth. To establish value in the physical world, we must first demonstrate value in the digital one.

San Francisco recently unveiled a statue designed specifically to be "instagrammable." The hope is that it can serve as a beacon for digital engagement and that the city's physical profile will, in turn, grow.

Chicago's Cloud Gate (the Bean) tells a different story. Built before Instagram existed, its reflective surface captured our natural tendency to admire our own image while conveniently framing us against the city skyline. It transformed how we viewed physical space.

The Uncertain Value of the Physical World

We already have a term that recognizes our two-world existence – screen time. The average American now spends over 7 hours daily on screens—that's 30% of our waking hours devoted to digital rather than physical experiences. For teens, it's even more dramatic, with many approaching 9 hours daily. We're literally measuring our lives by how much time we spend in each world, and the digital world is winning.

As more activity shifts online, irreducibly physical experiences are becoming more prized:

• Nature: The feeling of wind, water, trees cannot be rendered in pixels
• Food: We eat with our eyes, but you still can't get calories from an Instagram reel
• Live events: Being amongst people all focused on the same song, ball, or sermon still hits differently from a live stream
• Physical intimacy: The most human experiences remain embodied
• Wellness: Look at the explosion of gyms, pilates studios, and spas taking over retail storefronts. People realize that you can’t improve your physical health in the digital world.

The above are essentially anything that fulfills the needs of the human body – the irreducibly physical things we need to live. As this divide deepens, the "real thing" increasingly becomes something you need to be able to afford. For those who can't, digital life will serve as a suitable substitute.

My concern, however, is that we're collectively losing our ability to create, appreciate, and transform physical space. Each year I see architecture students migrate to tech because the barriers are lower and the impact seems higher – which have a direct correlation to securing economic security for oneself. Building digital products requires less capital, fewer approvals, and reaches more people faster than building physical structures. The financial upside is exponentially greater in the digital world.

Fellow substacker, , who writes the deeply insightful, , has described this phenomenon as the "human doom loop" – a cycle in which people stop connecting in real life, reducing the quality of in-person activities and the physical realm itself, further discouraging in-person activities, and so on. While Diana focuses on the social dimensions of this loop, I'm equally concerned about the downstream implications for physical space. As we invest less in real places, they degrade, further accelerating the migration to digital spaces.

The existence of parallel worlds is revealing a new social divide. We're seeing the emergence of two types of people – those who prefer the digital world and those who prefer the physical world. Call them digiverts and physoverts. Shapers of both physical and digital space should be aware of these distinct user groups.

Some people thrive in digital environments. They feel more comfortable, more authentic, more capable there. Others feel alive only in physical space, craving the sensory richness and embodied experiences that screens can't provide. This division often aligns with our generational bridge—Boomers and older Gen X tend toward physovert tendencies, while Gen Z leans digivert. Millennials straddle both worlds, often experiencing the tension between them most acutely.

What This Means for Those Who Shape Physical Space

If you design, build, or regulate the physical world, you compete with an entirely different reality than just half a generation ago. The playing field is far from level, and acknowledging this imbalance is essential for developing effective strategies moving forward.

This demands an urgent reprioritization of what matters for physical spaces in a digital age:

1. Design for what digital can't replicate: Sensory richness, unexpected encounters, sounds, smells, serendipity

2. Reduce friction: The physical world must learn from digital's accessibility without sacrificing what makes it authentic. Highlight accesibility.

3. Embrace nature and movement: Create spaces that use natural beauty to amplify built harmony

4. Build for both worlds simultaneously: The most successful physical spaces will have digital components that enhance rather than replace them

We need both worlds to thrive, each doing what it does best. The physical world offers presence, weight, and consequence, the ineffable feeling of being somewhere real. The digital world offers reach, efficiency, and possibility, the freedom to transcend physical limitations.

Understanding this competition is the first step toward a better balance. The second is designing physical environments that compete not by mimicking digital conveniences, but by doubling down on irreducibly physical experiences and making them more attractive and attainable than ever.

There are about 8 billion people on earth. In 1960, there were 3 billion. The implications of population growth for consumption, environmental impact, and urbanization are well discussed. But what's not understood enough is the obvious corollary. In two generations, global society has become nearly three times as dense.

Our entire planet has become dramatically denser, yet most of our policies, practices, and perspectives remain stuck in a less crowded past. The failure to adapt to this new reality is at the heart of our most pressing challenges, from housing affordability to climate change. Embracing population density, the proximity of people to one another, as a core lens could help us better understand and reshape our crowded world.

Planetary Reality Check

When William Anders took humanity's first full family portrait on Christmas Eve in 1968, he captured something profound: an image of encapsulated density. The photo accomplished what no map could, revealing Earth as an integrated system on a single object rather than an abstract realm. It demonstrated what everyone understood but had never actually seen: that we all must share the same planet. Earthrise showed us our blue planet as a whole object, finite, isolated, and complete.

But that family portrait captured a world with nearly 5 billion fewer people than we have today.

Earth hasn't grown physically in any meaningful way. There are about 148.94 million square kilometers of land. But the number of humans sharing it has exploded from 3 billion in 1960 to over 8 billion today. That's an incredible 266% increase in planetary density.

Let that sink in. How many lots, neighborhoods, towns, or cities can you think of that have almost tripled their density in two generations?

A Metric for Living Together

So how should we measure and understand this dramatic increase in planetary density?

The term ecology refers to the relationship between living things (not wetlands and living walls). A critical, if not the most important, relationship in the physical world is the distance between elements.

Looking at our planet through the lens of density reveals powerful insights. Rather than simply counting how many people exist, density forces us to consider how we exist together in shared space. This shift from absolute numbers to relative positioning unlocks a deeper understanding of our societal challenges.

When teaching Urban Design graduate students at Harvard, I'm often given absolute numbers as justification for their projects. But these numbers don't interest me. "Thicken the plot," I tell them, by introducing relative metrics over absolutes. Ratios lead to more questions to answer. They spur creativity, and they reveal relationships, dependencies, and dynamics. Of all the relative numbers, density is the most important for understanding human interaction at any scale.

Take New York City and the state of Arizona, each with roughly 8 million people. But while NYC packs those millions into just 300 square miles, Arizona spreads them across 114,000. That's a huge contrast: about 26,000 people per square mile in the city, compared to just 70 in the state. That single ratio, density, shapes nearly every aspect of life in these places. From transportation and housing to social interactions, resource distribution, and governance, the way people relate to space fundamentally reorders how society functions.

Density allows us to shift our perspective from quantity to quality. The number implies important social and power dynamics when overlaid with contextual considerations like culture, economy, and geography. The human question has never really been about how we live, but how we live together.

While we're busy arguing about whether to allow duplexes in single-family neighborhoods, a question I focus on in my professional life all the time, we should remember that the recent densification of the planet has profound implications.

Focusing on Proximity

Density measured per unit of area is useful for analyzing regions and economies, but it doesn't fully capture what it feels like to live somewhere. It tells you how full a place is, not how close people are.

The comment section of a recent post about my concept of Density Appetite made something clear—many people don't distinguish between density (a measurement) and crowding (an experience). Two New Yorkers, both of whom appear to be on the older side, and one of whom listed their job title as "Full-time Grandpa," began decrying how unbearably crowded areas of the city became and that policymakers were prioritizing increasing foot traffic over the pedestrian experience. The back and forth made me realize that for most people, what matters isn't how many people there might be in a square mile, but how close or how far away they are from someone and by extension how likely they are going to run into someone or have more space to themselves.

Average Human Proximity (AHP) is the average physical distance between individuals if people were spaced evenly across a given area. It's a simple metric I've come up with, limited by my rusty math capacity, that captures what traditional density measures miss - how close we actually feel to one another.

In 1960, the global AHP was around 222 meters (728 feet). Last year, it it had been reduced to 135 meters (443 feet). On average, every human on Earth is now one football field closer to the next one compared to just two generations ago.

AHP brings density to life in ways traditional metrics can't. It helps us understand why downtown San Francisco feels eerily empty post-pandemic despite unchanged building density. The structures remained, but the people left, dramatically altering the experiential proximity that defines urban vitality.

Let's go back to the city and the desert. New York's AHP is just 9.9 meters (32 feet) across the five boroughs, while Arizona's is 192 meters (630 feet) throughout fifteen counties. It is no wonder that stark differences in human closeness have profound effects on human ecology and, in turn, the forces that structure them, including planning, policy, culture, mobility, and politics.

Average Human Proximity also reveals temporal changes in density. Manhattan's daytime AHP during work hours is just 4.7 meters (15.4 feet), but extends to 10.4 meters (34.1 feet) at night as the commuter tide retreats. This fluctuation of 5.7 meters also demonstrates the dynamic nature of cities, like a heart that pumps population throughout a region. (Source: NYU Wagner Rudin Center, 2012)

I’m not surprised if this idea sounds familiar. During the pandemic, the concept of social distancing - two meters or six feet apart -imposed an artificial lower bound on human proximity. And while the pandemic may now be in the rearview mirror, our thinking about proximity shouldn’t be.

Density across Scales

Density and proximity do not operate uniformly across our world.

Instead, density can be understood across interconnected scales, from continent to dwelling unit, each with its own distinct characteristics, yet collectively forming a network of nested dependencies and ecological relationships. Neither area-based nor proximity-based density averages fully capture the local variation and uneven distribution of human presence.

We intuitively understand that people cluster more tightly in economic capitals than in regional hubs, in cities more than suburbs, and in subway cars more than parking lots. While direct comparisons between different units of area, such as square kilometers and square meters, can be difficult to grasp (like guessing how many beans are in a jar), it is possible to draw meaningful connections between these nested scales. AHP allows us to compare across scales using a single linear metric that aligns with human perception and proportion.

Global (geopolitical fuel): Density drives resource competition, migration pressures, and transnational challenges. Corollaries – GDP, immigration, workforce and market size

National (varied densities): Countries deploy density differently based on geography, culture, and economic systems. Compare Japan (AHP 36 meters) with Australia (AHP 371 meters), which represent entirely different approaches to organizing human space. Corollaries – eetro regions, climatic zones, electoral college

City (the image of density): Cities are where density becomes most tangible. Barcelona's sobre mesa-inducing fabric (AHP 20 meters) contrasts with Phoenix's sprawl (AHP 89 meters). Tokyo's AHP of 12.5 and Sydney's of 48 are well below their national averages. Unsurprisingly, people are closer together in cities. Corollaries – public transportation, infrastructure, sanitation

Neighborhood (community density) At this scale, debates emerge about "neighborhood character," parking, and building heights. It's where theoretical density meets lived experience. It is also the scale where irregularities in human proximity become the most contentious. The single-family homeowner protesting against the new multifamily development is also protesting against reducing the average physical distance between them and others in their community. Corollaries – FAR, zoning, design guidelines, setbacks, look and feel

Building (unit density): Housing markets and typologies lead to different proximities within buildings. Multifamily developments need to structure their unit mix along a range of parameters, including zoning, building code, financial structures, and market fit. Meanwhile, single-family residences market ample separation between the inhabitant and the next closest neighbor, with a picket fence for impact. Corollaries – typology, product type, layout efficiency, building code

Living Unit (personal density): The final scale is the individual dwelling, where density shapes our daily rhythms and personal space. Hong Kongers have only about 3.94 meters (12.7 feet) between them the next person in the same dwelling unit. An American household is much less crowded at an AHP of 8.24 meters (27 feet). Corollaries – Clutter, bunkbeds, garages, ADUs

At each scale, different concerns dominate. Global density can't be controlled directly, but all others can be shaped through policy, design, and culture. And since density is never distributed evenly, as we restrict area scale, we get more compressed.

Population Inflation

As planetary density increases, so does competition across multiple levels.

Cities battle for talent, investment, and cultural relevance.

Nations scramble for resources, influence, and economic advantage.

Individuals fight for housing, jobs, and even digital real estate.

Competition has grown keener than the 266% increase in world density since 1960. I want to call this phenomenon "population inflation" where the impact of each additional person on competition, resources, and opportunity outpaces their numerical addition to the population. Just as monetary inflation erodes purchasing power, population inflation diminishes the impact of each individual in markets, politics, and cultural spaces. Those who command the most attention have a global audience at their fingertips, but getting to the top is more difficult than ever.

We know that cities are as successful as the opportunities they create. As resources, opportunities, and attention become more contested, the intensity of competition has amplified beyond what raw population numbers would suggest, creating feedback loops that intensify pressure in desirable locations while leaving others behind. Access to cities is a scarce privelege in a denser, more competitive global society.

Recognizing population inflation and its impact on physical density is crucial if we hope to address today's challenges rather than yesterday's. Our policies and systems were designed for a world with different density pressures, and without acknowledging this inflationary effect, we'll continue applying outdated solutions to fundamentally transformed problems. Modern mobility has been made easier by shared borders, accessible air travel, and instant communication. Competition is no longer contained within national borders but radiates globally in real-time.

Engineering Around Density

As we grapple with this intensifying competition, we've developed technological solutions that attempt to mitigate or sometimes simply redistribute the pressures of density. Some create new challenges.

Remote Work: The pandemic forced a grand experiment in remote collaboration, with profoundly uneven outcomes. Cities that contained COVID-19 effectively (like in East Asia) maintained their physical work cultures. Western cities saw permanent shifts toward remote arrangements, essentially redistributing density from downtown cores to residential neighborhoods and exurbs. I've witnessed San Francisco's downtown transform from vibrant to vacant, not because buildings disappeared but because people did. Walking through the once-bustling Financial District now feels like touring an abandoned movie set—gleaming towers with empty lobbies, shuttered storefronts where lines once stretched around the block, and plazas designed for thousands now occupied by dozens. (This dramatic density collapse prompted me to run a studio at the Harvard Graduate School of Design focused on reimagining a future downtown San Francisco)

Digital Density: While physical density has tripled, digital density has exploded exponentially. Social media platforms concentrate billions of interactions in virtual spaces that didn't exist before. Algorithms determine which ideas gain visibility based on engagement density. Even as we physically spread out, we simultaneously crowd into digital environments that mimic and often intensify the competitive dynamics of dense physical spaces.

Globalized Production: We've engineered systems to move materials and products across vast distances, allowing manufacturing density to concentrate in specific regions while consumption spans the globe. This separation of production and consumption has profound implications for how we understand and manage density.

Density Changes Human Behavior

Every organism’s behavior is shaped by its environment.

Humans interact differently in groups versus individually. A revealing experiment by Ofer Feinerman, Tabea Dreyer, and their team at the Weizmann Institute of Science, compared how ants and humans navigate spatial challenges. When tasked with moving large objects through complex barriers, ant colonies consistently outperformed human groups. Their collective intelligence thrives in dense environments.

But when a single human faced off against a single ant on the same task, the human won handily. Our evolutionary success came from individual problem-solving, not collective coordination

Single Ant

Single Human

This paradox has huge implications for our dense world: unlike ants, who instinctively collaborate when packed together, humans tend toward individualism in crowded environments. The denser we get, the harder cooperation becomes. More considerations create more opportunities for discomfort. Ever tried to get a condo board to agree on a paying for a new roof? Now imagine scaling that to immigration policy.

I've come to recognize that I'm a bit of what you might call a "densoephile" and draw energy from the sights, sounds, and smells of human proximity. Subsequently, I've always found it easier to enter into dense situations than to withdraw from them. When I return to Hong Kong from San Francisco, or back when I was commuting to see my partner in New York while attending grad school in Cambridge, I feel energized rather than overwhelmed by the compression of humanity. But I've observed many colleagues and friends who experience the exact opposite reaction, retreating from density with the same enthusiasm I bring to embracing it (time to admit, I don’t understand camping). These personal density appetites shape not just our individual experiences but our collective ability to adapt to our increasingly compressed world.

Our species evolved to do things our own way, not to live harmoniously in tight quarters. Yet here we are—8 billion individuals sharing a planet that isn't growing in size, facing problems that require unprecedented cooperation.

The Generational Density Gap

This challenge is further complicated by the fact that those making decisions about our dense world formed their worldview in a much less crowded one.

A clear spatial consequence of our current gerontocracy is the political establishment has a bias toward sparsity. What’s the significance of 1960? This moment marked the convergence of post-war recovery, the acceleration of modern technology, and the birth year of many who now hold power and property. It's when our current economic and political systems were being solidified.

The average U.S. Senator is 65 years old, the average Fortune 500 CEO is 60 (Madison Trust: Fortune 500 CEO Ages), and the median world leader age is 62 (Pew Research: World Leader Ages). All were born around 1960 when Earth held just 3 billion people. Our decision-makers’ formative years occurred in a world less than half as dense as today's.

Nostalgia plays a powerful role in how we make decisions. Research shows that it functions as a cognitive shortcut, shaping present preferences through emotionally idealized memories of the past (Sedikides, Wildschut, & Baden, 2004). The global, national, and local densities that leaders instinctively reference often reflect the conditions of their upbrinings, not current realities. As cities evolve, these outdated mental models persist, anchoring decision-making in a density profile that is more memory than reality.

Is it any wonder that our policies seem disconnected from the pressures of today? In America, an increasingly older ruler class is governing a world that is denser and more complicated than ever before. From infrastructure investment to housing policy, transportation systems to urban planning, their mental models remain anchored in the spatial realities of previous generations. This entrenched spatial conservatism manifests as resistance to necessary adaptation, leaving us with cities designed for a population density that no longer exists.

This concept also passes the eye test. As we age, we naturally prefer less density: more space, fewer stairs, and more peace and quiet. This biological preference, combined with outdated mental models of "normal" density and the consolidation of resources and influence in older populations, creates a perfect storm of resistance to the very adaptations our cities need most.

We face a delicate challenge: honoring the wisdom that comes with age while acknowledging the limitations it can impose on future-oriented decision-making. When power is concentrated in the hands of those whose formative experiences were shaped by a fundamentally different density reality, it creates blind spots precisely where clarity is most needed.

Density Denialism

Despite this planetary compression, Western cities are increasingly resistant to adapting. The physical environment of the West has shifted from growth and dynamism to preservation and exclusion.

Restrictive Zoning: Compare Barcelona's urban fabric to most American cities. Barcelona's open grid embraces density while maintaining livability. Most American cities lock down development potential through complex zoning regulations that prevent adaptation.

The Exclusivity Mindset: There's an unspoken belief in many Western cities that they've "figured it out" and are already desirable, so why change? This morphs into a culture of exclusivity, where controlling who gets to live there becomes more important than growing the city itself. There's also a sense of "out of sight, out of mind." Westerners are largely unaware of the building advancements occurring around the world.

Building Culture in Decline: Our post-war construction is aging rapidly, yet we expect these deteriorating structures to appreciate in value. Other regions build quickly and create buildings of superior quality. In my experience as an architect, sometimes the only thing harder than building a new building in California or Massachussets is tearing down an old one, trapped in red tape and historic preservation battles.

Field vs. Pointal Verticality: Cities like Seoul, Shanghai, and São Paulo embrace "field verticality," where height is common rather than exceptional. Western cities often resort to "pointal verticality," isolated towers designed for iconicity rather than ecosystem development. As the urban scientist, Ramon Gras once commented to me, "the American model of urbanism is essentially to have a Manhattan at the center of a Phoenix."

Overall, the West has developed a bias for, depending how you look at it, inaction or for preservation of low density. While America's population hasn't grown at the same rate as the global population, it has still nearly doubled since 1960 (180 million vs 340 million). Meanwhile, the world is now 60% denser than when I was born and 300% denser than when my parents were born.

Fast vs. Slow Metabolisms

This resistance to density adaptation isn't uniform globally. Different urban centers respond to population pressure with dramatically different metabolic rates.

Rem Koolhaas, the Pritzker Prise winning architect (and my former boss) framed this contrast through the concept of the Developmental City, which he describes as urban environments where ambitious top-down planning leads to a metabolism of growth that outpaces traditional planning constraints in pursuit of rapid modernization economic development.

Not all cities approach density the same way:

Many Western cities are quickly resembling hardened fossils in that you can easily tell what they once were, but they lack the material to demonstrate what they are or will be. Meanwhile, developmental cities, from Lagos to Jakarta to Shenzhen, operate with an unstable equilibrium where construction, demolition, and reinvention are continuous. Their urban fabric is less a static monument than a living system.

Despite the dramatic increase in global density, the source of that densification is unevenly concentrated in the developing world.

The Growth Paradox

Our economic systems demand perpetual growth while operating on a planet with fixed resources and increasing density. More mouths to feed, more jobs to create, more shareholder value to increase, and all tying back to the density equation.

The consequences of this population increase crash against the reality of finite space. We've created economic systems that require endless expansion on a planet that doesn't grow.

Thinking in terms of density rather than just population forces us to confront these relationships. Density transforms population growth from a purely economic question into an eco-social one.

I don't think people really thought about density in the 1950s and 60s. They were too busy building modern society or trying to prevent us from destroying it. If the 20th century was about unconscious increases in population, the 21st century is about managing density. Even in regions with declining birth rates, density is still increasing locally as people move to cities and economic centers concentrate.

Heat

When Anders captured Earthrise in 1968, he showed us a world that seemed vast and full of possibility. If he took that same photo today, what would we see? Not just a more crowded planet, but a more connected one, a world where the distances between us have collapsed and our mutual dependencies have multiplied. We are more compressed.

This compression is making our planet hotter—and not just in the climatic sense. In a heat pump, when molecules are compressed, their density increases, pressure builds, and heat is generated. Our society works similarly. As we compress humanity into less relative space, we generate social heat through competition, friction, and intensified interaction. The higher the pressure, the more heat produced. We see this manifested as heightened competition for resources, housing, opportunities, and attention. If there is too much pressure, the system can collapse.

Yet this heat isn't entirely negative. Just as a heat pump harnesses compression energy for productive purposes, we need to channel our social density into constructive outcomes. Our economies require population to function, but they also need space for people to live, work, and thrive. Managing our density situation means, providing adequate housing, services, and infrastructure, expanding our capacity to accommodate the compression rather than fighting against it or allowing the pressure to build unchecked.

Peak Density

The world is expected to reach peak density in 2100 when the population hits 10.2 billion at an AHP of 120 meters.

This compressed future demands that we develop sharper spatial intelligence, or the ability to comprehend three-dimensional relationships and their human implications. As someone who trains young urban designers, I've witnessed how design education is having a harder time developing this critical skill, despite purporting to do so well. I’m concerned that instead of focusing on spatial intelligence, we've been distracted by peripheral goals, leaving us with a generation who lack the conceptual tools to navigate our increasingly dense reality.

Our future depends on leadership that understands density not as an abstract concept but as the fundamental organizing principle of 21st-century civilization. We need decision-makers who can see across scales, from global to personal, and dimensions, from social to physical, and craft policies and lead towards our denser reality.

What's particularly concerning is how younger generations, who have never known a less dense world, are navigating this reality. Many are retreating from physical gathering spaces into digital ones. This bifurcation between our physical and virtual existences may represent one of the most significant adaptations to our compressed planet, though not necessarily a healthy one.

The most profound challenges of our era, which include housing affordability, climate change, social polarization, and resource competition, all connect back to how we choose to live together in an increasingly crowded world. Earthrise showed us our planet as a shared home. Now, as that home accommodates more than twice the family it held then, we must reimagine how we organize our collective life within its unchanging continents.

Fundamentally, understanding density gives us not just a diagnostic tool but a prescriptive one. It reveals that our most significant challenges stem from our collective choices: how we work together, how we share space, and how we organize our communities. By embracing density as our core lens, we can transform our compressed planet from a source of conflict into a catalyst for innovation where cities, systems, and societies benefit from healthy human proximity.

Housing is on everyone's mind these days. Whether you're a renter facing steep increases, a hopeful first-time buyer priced out of the market, or a city planner trying to address homelessness, the effects of our housing shortage can be felt across society. But as I discovered in a recent conversation with The Atlantic’s Yoni Appelbaum on my podcast, Most Podern, there's another troubling dimension to this crisis: Americans are increasingly "stuck" – unable to move to places of opportunity.

Appelbaum's new book, Stuck: How the Privileged and the Property Broke the Engine of American Opportunity, examines how America shifted from a nation of movement and reinvention to one that has grown increasingly static. I cannot recommend this book enough—it is critically researched and beautifully written. My co-host, Libo Li, has written his own review, and I want to address some of its main points while expanding on the conversation.

Watch our interview with Yoni here:

America’s Mobility Crisis

"For 200 years, Americans moved from the poorer parts of this country toward the richer parts," Appelbaum explained. "That has reversed. Now they move from the richer parts to the places where housing is cheap."

This reversal represents a fundamental shift in American life. Historically, geographic mobility wasn't just about changing locations – it was the mechanism through which people reinvented themselves and climbed the economic ladder. The freedom to move was the freedom to belong, to build new communities, and to pursue opportunity.

"Until 1970, one out of five Americans moved every year," Appelbaum noted. "We just got new numbers from the census. It's down to one out of 13. It's an all-time low."

This decline in mobility has measurable effects. "When people move... they become more optimistic. They are likelier to see that the gains of others lift all boats. The people who wanted to move and then didn’t... grow more cynical, more alienated, more withdrawn." Throughout our conversation, Appelbaum lays out the benefits of moving, from increased societal cohesion, to better aligning economic opportunities to individuals, to regularly rethinking engrained lifestyles. It was refreshing to think about a social practice with seemingly so many beneficial economic, community, and almost spiritual effects. The problem, though, ties to how we treat our built environment, especially around housing.

The Progressive Paradox

One of the most compelling insights from our conversation was what I'd call the "progressive paradox" – a fundamental contradiction at the heart of progressive housing policy. As Appelbaum put it:

"Housing regulations have largely been a progressive project, and so they are most restrictive and most avidly enforced in the most progressive jurisdictions. The tragedy is that those are also the places Americans most want to live because of the other aspects of progressive governance."

This observation struck a chord with my co-host Minkoo Kang, a developer, who remarked that these restrictive attitudes persist in community meetings: "There is a huge ignorance in terms of the scarcity of land and the cost of things." This is not an uncommon frustration with well-meaning developers like Minkoo. Individuals have outside influence on how places are shaped despite not knowing how that shaping takes place. Everyone’s a critic. It’s like the Yelpification of the neighborhood.

This paradox has gnawed at me for years. As an architect in San Francisco and an urban design professor at Harvard, I’ve seen firsthand how two of America’s most progressive cities systematically undermine their stated values through their housing policies. The sentiment has appeared here and there, but more and more people are talking about it in the wake of the 2024 elections.

As a practitioner and an observer, I'm very firm in saying that progressivism has been distracted by proceduralism – an obsession with process over outcomes. Community meetings, environmental reviews, historical assessments, and endless revisions have become how housing is delayed or denied. These meetings claim to provide 'community input,' but in practice, they serve as de facto veto points for housing projects, prioritizing the loudest and most entrenched voices over actual needs. Come to a public meeting on affordable housing and you will know what a vetocracy feels like. On a systems level, progressives prefer one where every concern must be accounted for, every objection addressed, with complete agnosticism toward actual results.

Recalling the NIMBY anthem:

Lift every voice and complain,
'Til the architect and developer disdain,
Making their toil and their work be in vain.
Let our objections rise,
Loud to the city skies,
Not in Our Backyard as our sacred refrain.

The Broader Scope of the Progressive Paradox

Beyond zoning, several progressive policies contribute to America’s mobility crisis. While we discussed many of these on the Pod, there are even more contradictions within progressive housing policy that we didn’t have time to explore. These additional barriers further reinforce the paradox of progressive jurisdictions advocating for inclusion while enacting policies that lead to exclusion.

Rent Control

Rent control is often positioned as a tenant protection measure, but it fundamentally subsidizes demand rather than increasing supply. By capping rent increases, these policies discourage new construction and renovation of existing buildings. Landlords have little incentive to improve properties when returns are artificially limited.

Unlike Phoebe's grandmother's apartment in "Friends" (which became a running joke for its unrealistic affordability), most rent-controlled units aren't passed down through generations. Instead, they create perverse incentives that keep people in housing that may no longer suit their needs simply because they can't afford to move – another form of being "stuck."

Union Labor and Construction Costs

Another progressive value – supporting unions – comes with trade-offs in housing policy. While union labor provides important protections and fair wages for hard-working contractors and subcontractors, it also adds a significant premium to construction costs, often upwards of 30% to total development costs.

More concerning is the active resistance many construction unions have shown toward modular construction – a potential solution for more affordable housing. Modular construction has been stifled in the Bay Area (The Economist) – if it can't find product-market fit in the most technologically advanced and housing-starved region of the country, where can it? Recent YIMBY legislature such as California's SB-4 (the so-called "Yes in God's Back Yard bill), require prevailing wage labor. Given the cost of construction, its uncertain if such policies will actually spur more development.

I also think its valid to note an important reality: the incentives of the construction industry don't align with housing abundance. Scarcity drives up the cost of their services, benefiting their bottom line. This isn't to vilify unions or contractors – businesses naturally pursue profit – but we must acknowledge that these incentives work against goals of creating more affordable housing.

The 30-Year Mortgage

The 30-year fixed-rate mortgage is an American innovation that provides homeowners with remarkable stability. Unlike many countries where adjustable-rate mortgages are the norm, Americans can lock in their housing costs for decades. It is not a progressive policy, but it has been an important tool of the middle class – a group that progressivism is increasingly losing.

However, this creates another form of being "stuck." When interest rates fluctuate dramatically – as they have in recent years – people who secured low rates become reluctant to move, even when their housing no longer suits their needs. A family that has outgrown their home or needs to relocate for work opportunities might choose to stay put rather than double their monthly payments with a new mortgage.

America should consider making mortgages more portable or transferable, allowing people to carry their favorable rates to new properties, enhancing mobility rather than hindering it.

Class Above All: The Evolving Image of NIMBYism

In progressive discourse, NIMBYism is often framed as a problem of racist and aging homeowners. While Yoni expertly traces zoning's racist origins in our conversation, he also notes how exclusion has evolved. What began as explicitly racial segregation has transformed into economic segregation—a class-based system that achieves similar results through different means.

Today, "Not In My Backyard" really means "Don't Touch My Net Worth." It turns out that the most effective way to convert a progressive into a conservative on housing is to hand them a mortgage. When housing becomes an investment vehicle first and shelter second, people of all backgrounds will fight fiercely to protect their property values.

I witnessed this firsthand while developing a 100-unit affordable housing project in Hollister, California. At CO-, the office I started with my partner Weijia Song, we're handling both development and architectural design, an integrated approach that's uncommon but delivers better, more affordable housing by eliminating the inefficiencies of siloed processes.

When we presented to the planning commission (watch the video here), the opposition wasn't from white boomers but predominantly young people of diverse ethnic backgrounds who had recently bought homes nearby. "We were told this would be a park," one neighbor insisted. "How will our children be safe?" asked another. The catch was this lot was designed for high-density affordable housing over twenty years ago, long before the homes that their owners were looking to protect were even built.

These neighbors, perhaps themselves first-generation homeowners, had bought into the American dream where homeownership equals wealth-building. They were simply protecting their investment using the same exclusionary tools that may have previously deployed against their own communities. Minkoo has been fighting a protracted fight under similar circumstances in Boston’s Roxbury neighborhood, to get his client’s project accepted by the local community.

This reveals the most insidious progressive paradox of all: in a system where housing is primarily a wealth-building mechanism, even those who have historically been excluded will, once included, fight to maintain the exclusivity that gives their investment value. The problem isn't demographics – it's that we've structured housing to reward scarcity rather than abundance, exactly as Yoni argues has happened across America's most desirable cities.

The Path Forward

The biggest roadblock to housing abundance is what I call 'construction constipation'—a system where permitting drags on for years while the actual building process takes months. This inefficiency doesn’t just drive up costs and stifle production; it saps energy and momentum from those trying to solve the housing crisis. The longer we allow these bottlenecks to persist, the further we entrench the very scarcity we claim to be fighting.

The good news is that we may finally be turning the page toward policy clarity. One promising solution is 'as of right' construction, as Appelbaum suggests: 'If you publish clear guidelines, and as long as you stay within them, you can just build.' Predictability and accountability go hand in hand in the development process, and ensuring a straightforward path to building would eliminate many of the barriers that have slowed housing production to a crawl.

There are signs of a shift. As I mentioned to Appelbaum, even planning commissioners are now challenging old assumptions: "You shouldn’t be worried about affordable housing making your neighborhood unsafe. You should be worried about whether your kids will have a place to live when they’re 25 or 30." But shifting attitudes alone won’t get us there—we need bold, responsive leadership. And ideally, that leadership should come from a generation that hasn’t yet paid off their mortgage, one that understands firsthand the frustration of being locked out of homeownership and the urgency of housing scarcity.

Getting Unstuck

Addressing America’s housing crisis requires an honest reckoning with its contradictions. Progressive values of inclusion, diversity, and opportunity should align with policies that enable more housing, not less. If we are serious about restoring the engine of American opportunity that Appelbaum describes—the one that once allowed people to move freely in pursuit of better lives—then we must abandon policies that entrench scarcity and exclusion.

We are at a critical juncture. Ezra Klein and Derek Thomas’ new book, Abundance, drops this week, and they’ve been making the rounds on liberal media, pushing its ideas and potential. In a moment when liberal leadership is so clearly MIA—misaligned, ineffectual, and aloof—Klein, with his large following, appears poised to champion a new liberal cause centered on productivity. But as much as I want this to land, I’m not convinced his value proposition will resonate where it matters most.

On one hand, if progressive politics is truly about inclusion, then housing abundance should be non-negotiable—surely, someone will right this ship. Yet, the paradox is undeniable: a system that preserves privilege under the guise of protection. As Stafford Beer observed, “the point of a system is what it does”—not what it claims to do. If our housing policies produce scarcity, exclusion, and stagnation, then those outcomes are the system’s true purpose, whether or not progressives admit it. A reboot won’t happen without realigned incentives.

And yet, the housing crisis exposes liberal contradictions in a way voters can no longer afford to ignore. Over the past decade, I’ve learned one undeniable truth: America can tolerate liars, but it despises hypocrites. The path forward is clear. By confronting this paradox head-on and enacting policies that prioritize housing abundance over ideological purity, we can create cities that are both economically dynamic and truly inclusive. The choice is ours: double down on the contradictions that have stalled mobility or build the future we claim to want. There is no time to waste.

Do you feel like your city isn't what it used to be, but you can't quite pinpoint why? Maybe it's the proliferation of "For Rent" signs, the increasingly chaotic transit system, or the aisles of the local pharmacy beginning to resemble the deposit boxes of a Swiss bank. Perhaps it's the solitary construction crane that seems visible from every neighborhood, a harbinger of stalled growth.

Post-pandemic, urban issues have become starkly visible. Many sense that their cities are faltering, but is this just a rough patch, or are deeper structural issues at play?

It's hard to believe the dreamlike reality of the pandemic began five years ago. Since then, cities have faced unprecedented challenges — environmental volatility, a once-in-a-century global health crisis, and economic and social shocks that have reshaped urban life. Some cities have adapted, finding new ways to thrive. Others, however, have lost their way, unable to keep up with shifting realities.

Cities rise, thrive, and sometimes decline. But decline isn't always obvious at first. It starts with small warning signs: delayed maintenance, endless permitting delays, a growing divide between rich and poor. Over time, these cracks widen until one day, the city itself feels unrecognizable. In cities worldwide, the pandemic widened these faults, giving the impression in many places that the decline happened all at once.

To help assess whether your city is on the right track or heading toward decline, I've developed a simple framework: The Four Horsemen of Urban Decline. Spotting one is a warning. Two means trouble. Three is a full-blown crisis. And four? Your city isn't just stagnating—it's probably actively driving people away.

I'll admit, I developed this framework partly out of exasperation. I've visited all sorts of places over the years and seen both successes and failures. But in the years after the pandemic, I've grown tired of watching the same patterns of decline repeat themselves while leaders insist everything is fine. There will always be black swan events that exacerbate issues, but these events tend to intensify bad habits, not create them. At this moment, I think we need to put a face to urban failure.

1. The Disease of Me

The first horseman gallops in wearing the gilded armor of past triumphs. I borrowed this concept from nine-time NBA champion-winning player, coach, and executive, Pat Riley, who observed that previous success often becomes the greatest obstacle to future achievement. Players focus on individual stats and contract negotiations rather than team success, and the championship chemistry dissolves. Past success can also be a city's largest immediate vulnerability.

When a place thrives for too long, it starts to feel inviolable. San Francisco in the 2010s was a prime example. The tech boom brought unimaginable wealth, businesses flourished, and optimism reigned. However, underneath, housing shortages, homelessness, overreliance on the tech industry, and a deteriorating public realm were not getting enough attention. When the pandemic hit, the city's latent fragility was exposed.

A+ cities like New York, London, Hong Kong, and Sydney can suffer from similar hubris. They pride themselves on being the greatest cities in the world, assuming people will always want to live there. However, as remote work reshapes professional life and affordability declines, that assumption is being tested.

I remember moving to New York and experiencing the Disease of Me in action. Waiting for the A train on 8th Ave and 23rd Street, I'll never forget overhearing someone amazed at how "cheap, clean, and fast" the New York subway was. At the risk of sounding snobby, I’ll say this. Yes, the NYC subway is convenient, given no other option, but no resident of Shanghai or Berlin would echo this statement I heard on that platform.

I'm describing urban solipsism, which means city leaders, businesses, and longtime residents, thinking that the way their city is is the only way it ever can be, become more focused on protecting what they have than improving for the future. That unending bullishness can lead cities to violate two fundamental fiscal principles—one from Wall Street, and one from the streets:

1. Never spend the principal

2. Don't get high on your own (housing) supply

Outside fo finances, this unchecked confidence affects a city's ability to function at every level. When leaders refuse to acknowledge that their systems are broken, they create a culture of inaction. This is especially evident when it comes to actually building something new. What happens when a city needs change but can't physically execute it?

2. Construction Constipation

Yes, it's not a pleasant image. But neither is waiting two years for a building permit.

I will save you the embarrassment of asking your doctor and tell you the medical definition of Construction Constipation : When it takes longer to get a permit than to build the actual structure.

When cities experience this kind of sclerosis, nothing gets built. Consider the permitting timelines across different cities:

Tokyo: 2 months (a mild inconvenience, but manageable)

Copenhagen: 6–8 months (frustrating, but expected bureaucracy)

New York: 12–14 months (painfully slow, bordering on absurd)

San Francisco: 24 months (soul-crushing, FML)

At a fundamental level, this bureaucratic inefficiency prevents cities from treating their own ailments through physical transformation. Construction is already a slow, arduous, risky, and costly process, so further policy-induced lag can make it actually impossible for housing and infrastructure to keep up with demand. And at today's interest rates, every unnecessary delay costs thousands, sometimes millions, in financing costs. Who pays for that? The consumer, AKA the young couple trying to buy their first home, the school district struggling to modernize classrooms, or the small business that just wants to open its doors.

On a psychological level, let's also point out that Red tape isn't just frustrating, it's enervating. When bureaucracy overtakes buildings, rules become weapons to block change rather than tools to facilitate it. If a city can't build, it can't adapt.

A clear solution? A permitting shot clock. If an application isn't processed within a set timeframe, it's automatically approved. This creates accountability and ensures that change isn't stalled by procedural ossification. Civic leadership may not be able to develop projects themselves, but applying pressure on the agencies who permit and authorize physical development is a low-hanging and common-sense maneuver that would be politically popular.

But when change is resisted, the consequences ripple across the entire economic structure, not just stopping at development. If a city can't build housing, infrastructure, or active spaces fast enough, wealth becomes further concentrated among those with access, while those without resources are left behind. This is how the third horseman arrives.

3. High Capital Contrast

Behold a figure split in two, one side draped in luxury, the other in destitution.

A city where extreme wealth and poverty exist in stark, unavoidable proximity is a warning sign of urban distress. When economic inequality so clearly fails the eye test, it leads to demoralizing bewilderment that grows over time, I call this high capital contrast.

Take San Francisco's Mid-Market district, home to the now-abandoned Twitter headquarters and amenity-filled apartments catering to high-earning tech workers. Just steps away, as goes the old real estate refrain, open-air drug markets thrive in the Tenderloin. Let’s call this the Twitterloin effect or the visceral collision of extreme wealth and extreme poverty that is impossible to ignore.

This phenomenon isn't unique to San Francisco and is particularly acute on the American West Coast. Visible imbalance breeds resentment, social instability, and the sense that something is fundamentally broken. You also see this dynamic in developing contexts, like the super-tall mansions of Indian elites overlooking sprawling slums or the famous image of luxury Paulistan condos built directly adjacent to a favela.

High capital contrast is also a sign of inefficiency. The 'E' word has become divisive of late, thanks to the disruptive antics of DOGE, but efficiency remains a goal worth striving for in almost any context. The ability to do more with less allows cities to reinvest saved resources—whether money, time, or political capital—into other priorities. The more reinvestment can occur, the more benefits can compound.

Wealth inequality is not inherently the issue, but rather, stark, jarring disparity is. Cities will always have contrasts, economic class being one of them, but when that contrast becomes too extreme, it shifts from coexisting with different kinds of people to merely enduring their proximity. Cities should not normalize this condition. To respond, they must actively work toward abundance, ensuring that opportunities and resources grow rather than resigning themselves to managing extremes. Furthermore, the image of such high capital contrast yields a childishly naive yet fundamental question. What kind of place is this? A city caught in this contradiction struggles to establish a clear vision, setting the stage for the final horseman—an identity crisis.

4. Identity Crisis

A city without a clear vision is doomed to drift. This is the identity crisis—when a place no longer knows what it stands for or where it's going.

Many cities today talk out of both sides of their municipal mouths:

"We need more housing!" they proclaim while making it impossible to build any.

"We embrace innovation!" they declare while fighting every change to the status quo.

"We want economic growth!" they insist while taxing businesses into exodus.

A city must evolve while maintaining its core essence. Last week, I discussed how cities should approach their Density Appetite, recognizing it as a defining factor in shaping their urban identity. A great city knows what it is and where it's headed. This involves being both physically conservative and progressive, striking a balance between progress and preservation. A declining city waffles between conflicting interests, paralyzed by indecision and nostalgia. This is where strong and effective leadership really matters and the cities I worry about most are those where leaders can't articulate a clear vision beyond vague platitudes.

The most confident cities build upon what has worked while adapting their identity to suit the current moment. Some of the most enduring places thrive in contradiction—London is both old and new, Hong Kong is both East and West, and Rio embraces both mountains and beaches. Rather than suffering from an identity crisis, these cities find strength in their dichotomy.

How do you test for a lack of identity? Poll a diverse group of people and ask them what the city should be. Some variation in responses is natural—even healthy—but when the answers are wildly discordant, it signals deeper uncertainty. A city with no clear sense of itself struggles to act decisively, leading to inertia, conflicting policies, and an inability to adapt to change. Without a unifying vision, progress stalls, and stagnation takes hold.

Recognizing the Signs—and Reversing Course

Cities don't die by accident. They decline through neglect, denial, and a failure of imagination. Recognizing these four horsemen isn't about giving in to despair—it's about diagnosing the illness before it's too late. Cities are not static; they are living organisms that can heal and become stronger. Some places and their inhabitants will deny these problems until they are irredeemable. Others will rise to the challenge, making bold changes to ensure their relevance and resilience. The most dynamic cities will take control of their future rather than become victims of it.

So, how does your city stack up? Are people working to fix it, or are they making excuses? This framework is designed to be accessible to anyone, combining sentiment, anecdotes, and data to provide a clear picture of urban health.

I encourage everyone to start conversations about what's happening in their own cities and in those they visit or admire from afar. Pay attention to the patterns. How many horsemen have arrived? Set a quarterly check-in—track changes, notice trends, and discuss solutions. Cities don't fix themselves. The difference between decline and renaissance is whether people recognize the signs early enough—and choose to act.

Growing up in Hong Kong, I thought density was normal. Seven and a half million people stacked in a vertical metropolis that makes Manhattan look spacious. Then I went to college in Texas, where single-family homes stretch endlessly across vast open land. The contrast made me wonder why some places are dense, and others aren't. There is no single reason for this discrepancy and include environmental, cultural, economic, and historical factors. But it's valuable to address these interconnected elements, which is why I'm introducing the term "density appetite."

Density isn't just a statistic. It's primarily an attitude. Tokyo eats density for breakfast. San Francisco nibbles at it like avocado toast after yoga. One city sees people per square mile as fuel for innovation; the other sees it as a threat to "neighborhood character."

Density Is a Choice

Plot twist: I'm not a density absolutist.

Density comes with tradeoffs, and not every place needs to maximize it. Density pluralism makes for a more interesting world and allows people to find the living environment that suits them best.

What I do advocate for is awareness—understanding that density is the source code of urban life and that it determines how everything plays out:

• Look and feel

• Housing affordability

• Transit viability

• Economic opportunity

• Environmental footprint

• Public space activation

• Impact on the natural world

The key is knowing when and where density makes sense. Geography and history matter, but policy, culture, and sentiment matter just as much.

The Growth Gourmands

Some places have insatiable density appetites:

Tokyo: Despite being one of the world's largest and most productive cities, Tokyo has kept housing costs relatively stable through consistent building. Housing supply meets demand because zoning allows it. Tokyo's flexible, incremental upzoning keeps housing in sync with its economy, serving as key economic and cultural fuel.

Paris: Maintains its aesthetically coherent, walkable density while strategically growing at its edges (shoutout to the Grand Paris Express). Hausmann's renovation wasn't just about beauty—it was about structured intensity.

Singapore: Density is a public (even national) resource. The city-state's public housing system accommodates 80% of residents in high-rises that are the envy of every housing advocate. Planned density yields planned openness, integrating transit, green space, and public place into an organized urban assemblage.

These cities don't just tolerate density, they leverage it as their unique value proposition. Their high metabolic rates, how quickly they rebuild, process change, and regenerate themselves, allow them to adapt to new needs rapidly. Their density strategies become signature elements of their urban identity and economic success. In each case, policy translates to lifestyle, and residents accept smaller dwelling sizes as a reasonable trade-off for living in these desirable environments.

Rent Too High? Move to Singapore - The New York Times

The Picky Eaters

By contrast, places like Sydney, Vancouver, and Los Angeles have some of the lowest-density appetites despite booming economies.

California, in particular, has a strange relationship with density. Perhaps it's the state's deep cultural association with individual freedom and the open frontier, or it's about preserving its stunning natural beauty. Either way, it's one of the world's most dynamic economies, yet it often refuses to grow in a way that supports its success.

Nowhere is this contradiction more glaring than in Silicon Valley. The region leads the world in technological breakthroughs, where engineers can fit billions of transistors onto a single semiconductor. Yet, regarding land use, San Jose, Cupertino, and Mountain View can barely fit five housing units on a single acre!

Geography Isn't Destiny

Density is contextual. A city's natural and historical conditions influence how it approaches density.

Land-limited cities (Mumbai, Manhattan) build up by necessity. Sprawling regions (Houston, Dubai) grew around cars and cheap land. Pre-car cities (Kyoto, Barcelona) inherited walkable density.

But culture overlays geography. Tokyo and San Francisco both face seismic risks and geographic constraints. Tokyo's higher metabolic rate means it builds continuously, replacing structures every 30-40 years and keeping housing costs relatively stable despite high demand. San Francisco's slow metabolism results in a city that fancies itself as a museum rather than a living organism capable of change.

The Density Decision

Cities need to define their density appetite to define themselves. At the one-quarter mark of the 21st century, every city needs to answer one question: How hungry are you?

One of the benefits of measuring density is that it distills a simple relationship—the number of people per unit of area. Short of creating more land, density is controlled through population size.

There are plenty of cities willing to do what it takes to maintain a healthy density. Meanwhile, there are plenty who are confused. San Francisco, where I live, is that thirty-five-year-old friend who complains that after a decade and a half of dating, there still aren't enough good choices out there. It wants economic dynamism, affordable housing, and transit options without the physical growth to support it. It defines itself by what it doesn't want to be: New York, Chicago, Los Angeles. San Francisco constantly talks about housing but never says how many people it actually wants. A million residents by 2040? 1.2 million? Without a target, there's no way to measure success—or hold anyone accountable. As the saying goes, you play to win the game - unless you can't decide on what constitutes a winning score.

With a defined growth target, tradeoffs could be evaluated rationally. Infrastructure investments make sense. Zoning changes have purpose. Resistance to development could be framed within an overarching goal.

Target population numbers would bring some much-needed consensus to complex urban concerns. They would also serve as the foundation for professionals to mobilize towards. Architects could propose physical solutions, developers financial strategies, and planners policy changes to get us there. Such a target would be a welcome change from the ten-way tug-of-war that is the process of getting anything built in so many stagnant jurisdictions.

Are We Getting Hungrier?

Density is no longer optional in many cities. Climate change, economic pressures, and shifting demographics force places to reconsider their stance on growth.

That doesn't mean that every city should max out its density. But far too often, cities dismiss density outright instead of considering how it can be used to make situations better.

The psychological condition known as NIMBYism (Not In My Back Yard) is often at play—driven by a fear of change and mistrust that new development will benefit existing residents. Yes, high-trust societies have an easier time demonstrating how urban transformation can improve everyone's lives (have you seen Copenhagen lately?). But especially in struggling cities, communities need to ask if their self-imposed density diet and slow metabolic rate—their inability to process and adapt to change—is starving their own future. Higher-metabolism cities make mistakes faster, but they also correct course more quickly, making them more resilient to economic shifts, population changes, and climate pressures.

We Are What We Eat

The density decision isn't academic, it defines our habitats and their inhabitants. It shapes how we move, work, socialize, produce, and consume.

Cities that refuse density in the face of need don't stay the same. Even worse, they fall behind economically and culturally. Those that build without purpose risk emptiness and obsolescence. The point isn't that every city should maximize density, but that each should intentionally choose its growth pattern rather than drifting into stagnation by default.

So what's your city's density appetite? Is it hungrily building for growth, reluctantly picking at development proposals, or starving itself into irrelevance?

Reply or share this with someone who has strong opinions about their city's growth. Let's put density on the menu.