The Mathematics in Support of Urban Density

A recent article in Full Stack Economics explains that the strongest case for urban density isn't aesthetics: it's math! 

Conversation about land use and building in cities often turns to questions of aesthetics or personal preferences. You find impassioned advocates of various kinds of architecture or lifestyle.

Opponents of density insist on the merits of big yards, or claim that multifamily buildings are eyesores, or get into minutia about how certain types of buildings spur gentrification.

Some folks on the pro-density side are equally aesthetic-minded. They paint a picture of biking in dedicated lanes past cute row houses along narrow, lively streets filled with people and not cars.

My sympathies are with the pro-density side of this argument. But I see the aesthetics as beside the point. To me, it’s just math. The biggest virtues of denser cities flow from ironclad principles of geometry and arithmetic—along with some basic economic concepts.

Affordability is the number of homes

You can house, at most, the number of people you build homes for. The more homes you build, the more people can afford to live in your city.

People in expensive markets who like to block new houses give you a lot of pushback on this point. They like to distinguish between “luxury” and “affordable” housing units, and they worry the market might supply too many luxury units and not enough affordable ones.

But this is a red herring. Markets have a lot of flexibility along quality dimensions. Residents, whether owning or renting, can occupy housing that might not have been intended for their income bracket.

What is much more inflexible is rigid, strict permitting. If your city only permits, say, 200 new homes, with 600 new bedrooms, it would be impossible for your city to satisfy 2,000 new residents.

In the end, the cities that build get the people. Compare, for example, San Jose and Houston. The San Jose metropolitan area has gained just under 500,000 people since 1990. Houston gained 3.8 million. And if you look at their building permits, it is extremely clear why. Each city added about two and a half people for every new unit it permitted over the period.

Read the full article here.