29 April, 2008

Zoning, São Paulo, and Density

Tyler Cowen recently sparked a minor discussion in the urban blogosphere about zoning. What would happen if zoning were less strict?

More specifically, Manhattan would look more like Sao Paulo, with a true forest of skyscrapers instead of the current puny and indeed embarrassing line-up. Many of these towers would be residential, as they are in Sao Paulo. Many problems of cities, including congestion, would of course become worse. Overall I see the gain as real but a small one, at least relative to gdp.
Reading this passage gives you the impression that São Paulo is denser than New York, however, Cowen is uncharacteristically wrong about this fact. According to Wikipedia, New York City has a density of 10,533/km² (including boroughs, so Manhattan is even denser), while São Paulo has a density of 7,233/km².

The deeper point here is that tall buildings do not imply density and so it is easy to be misled by pictures such as the one Cowen cites of São Paulo. This is not a picture of unplanned density; it is a picture of planned sparseness. True unplanned density means that there are tall buildings of varying sizes and many smaller buildings squeezed up against one another, not uniform buildings separated with ample space to breathe as in São Paulo. This picture indicates, rather, that great masses of people want to live incredibly densely, but that zoning laws have in fact forced these masses down and apart. Someone points out in comments on MR that São Paulo actually has fairly stringent height restrictions, which leads to the glut of 20-story apartment buildings. I imagine there are also rules about how close together these buildings can be. Thus, São Paulo looks more like a collection of housing projects than a real city.

Yglesias falls into this fallacy as well, though he makes the equally important point that lack of zoning does not imply density. Houston is an important example; there, lack of zoning has lead to more spawl.


aph said...
This comment has been removed by the author.
aph said...

Great Blog!

True unplanned density means that there are tall buildings of varying sizes and many smaller buildings squeezed up against one another, not uniform buildings

More often than not, developers of large buildings would acquire the smaller buildings to maximize value. The owners of the smaller buildings have the incentive to sell to the developer because they most likely won't be able to get as much value out of their property otherwise.

lack of zoning has lead to more sprawl.

How is that possible? Could you expand on that?
I do not think it is the lack of density/use restrictions that cause people to spread out. I would argue that overbuilding and subsidizing of socialized roads and parking are more the culprit.

Elliot said...

Good stuff. I just wanted to note Cowen's comment that congestion would become worse in denser cities. That would certainly be the case in our current paradigm, in which car use is de facto subsidized and (especially in cities that are not in the northwest corridor) there are few other convenient options.

But with the right mix of policies, that very "congestion" would not only be mitigated, but could become a net plus. People living closer to each other, and closer to where they work, would make public transportation much easier, reducing the number of cars on the road. Higher density is also more walkable - if what used to be a twenty minute drive is now a ten minute walk, that would have enormous implications for how people get around and interact within the city in ways that have many positive externalities. More lively neighborhoods and better health are just two I can think of.

Also, that photo of Sao Paulo looks awful. It looks more like a suburb than a city to me, in the sense that it appears to be almost all housing, with few shops, bars, offices, etc. Its the close mixture of many activities that makes cities appealing. I hope imitating sprawling Latin American mega-cities (some of the more dysfunctional in the world) is not our goal...

spencer said...

Thanks for your comment, Adam.

I didn't mean that small buildings would coexist with tall buildings, which typically doesn't occur for the reason's you point out. But a more "natural" outcome than large towers separated by green space is smaller buildings squeezed together.

Zoning doesn't have the same effect wherever it is used. It depends on how it is used. In Western cities where congestion is not an issue, zoning has typically been used to create density. In Eastern cities, the effect of zoning is usually to split functions, creating sprawl.

APH said...


I think the "natural" outcome could be what you are describing if it developed over a long time. However, if demand for housing was very high in a currently low density area, developers would buy up pieces and most likely build high-rises.
This is because above a certain density, it is more economical to combine services such as elevators and mechanic equipment, as well as the structural system into one building. It also allows they to optimize the floor plate. People prefer floor-plates in high-rises over floor-plates of long brownstones. There is a cost premium to vertical development , but developers sell/rent at premium as they go higher because of the views.

Could you describe how zoning creates density in western cities? Are developers being forced to build more dense than the market dictates? If that is the case, I don't know any developers who would willingly build there.

spencer said...


You're right, I was thinking about a long-term outcome. My point is just that people don't tend to demand lots of empty space or green space between high-rises, these tend to be features that planners put in. What is scarce in cities is space--yes, one way to get around that is to build higher, but there's no reason to build higher BEFORE you build closer together.

In Western cities, lots of forces already make cities spread out. Zoning would then be of less use for those trying to create sprawl; it is only useful for those trying to create density. This is perhaps why we see a relative lack of zoning in the West.