Monday, August 29, 2011

Urban Density Around the World

Matt Yglesias says
For one thing, it’s just not the case that some amazing technological breakthrough is required for people to have less gasoline-intensive lifestyles:
(From the units this looks rather like a natural gas graph but still the rough form of gasoline consumption would be similar so let's go with it for the sake of argument.) It's important to understand the reasons for these differences.  The graph above of gasoline consumption per capita is basically the inverse of this one, which shows urban density around the world:

I found the data here.  This is year 2000 data but changes since then will be modest (except possibly in China) - the figure is the average number of people per square kilometer in all urban areas of more than half a million people.

The places with the highest gasoline usage (like the US) are the places with lowest density and conversely places like India and China with very low gasoline usage also have extremely high urban densities.  It's this density that allows these kinds of things to work:
The technologies deployed in France—shorter commutes, lighter cars, trains, and buses—don’t require a massive R&D effort to implement. They require some investment in transit, they require a lot of changes to land use regulation, and they require people to receive a clear signal that saving money on gasoline by purchasing a lighter car and/or living closer to work is a good idea.
Indeed, shorter commutes and public transit are much easier if many services are close enough to walk, which depends on having enough people packed in walking distance of the store/bus stop/subway station, etc to make the thing economically viable.

So this is quite true, but it's also very important to understand that the present differences in urban density have taken a century (at least) to put in place and cannot be unwound quickly.  For example, if you are going to pack far more people into a given area you are going to have to make substantial changes in the housing stock (higher buildings, more apartments, etc) but the housing stock only changes slowly.  For example, from this piece, here's the ratio of housing units built to total housing stock in recent decades:

Note this data only goes through 2003 and I assume it must have gone off a further cliff since 2007.  Given that we only build 1-1.5% of the housing stock each year it's clear that the lifetime of the average housing unit we already have will be well over fifty years.  Therefore, the project of making US society a much denser more gasoline efficient place will be a very long slow one.  We don't have that long to address our oil dependency.

And so while the project of making US cities denser might not require much technological innovation, the project of making US consumers use far less oil within something like the current urban matrix probably does.


dr2chase said...

It would be useful to know how they define and measure "urban density". I tried a different approach -- looking at census data (on places with population of 50K or more) how many people live in places that are dense enough to support reduced car use?

Not only do we have plenty of places with European density, they are often agglomerated together (all the sub-50K towns surrounding Boston/Cambridge/Somerville, also have high density).

I think it makes more sense to target the easy case, rather than the average case.

kjmclark said...

"We don't have that long to address our oil dependency."

How long do we have? If all we build from now on is apartment buildings, would that do it? Combined with 20 years of Chevy Volts, constant improvements in rail, etc?

Seems like the biggest problem is that just-over $100 Brent prices don't seem to have sent a big enough signal.

theroachman said...

Interest chart I like the basic break down. You can use this for pollution too.

But I think Mexico and Brazil should be separated out from south and central Mexico into their own bar. They have much higher average density then the other countries of the region. Thus throwing off the data. But not by much.

Then of course you could even split the US up into regions too. Which may be over kill for what you where trying to show in the first place.

As for the apartment building and larger buildings, it seems to me, more of them would not cover the needs or even entice people to move into them they would have to be built entirely differently.

yvesT said...

Already said many times, but the first policy for the US should be to increase its quasi zero volume based gas tax

bmerson said...

Two points...

First, I read the Matt Yglesias piece (via Kevin Drum's blog) and immediately thought to myself, "Well, it also helps if your cities virtually all pre-date the automobile." Look at the cities in the US that are reasonably walkable and/or support a usable and relatively cost-effective public transportation system. They tend to be older cities like Boston, New York, San Francisco. Of course, even these places are now surrounded by suburbs and exurbs, strip malls and parking lots, but at least they evolved originally in a pre-auto world. That isn't really true for large swaths of the USA. Even while many of the cities may have core centers that pre-date the auto, most of the current city area was created during the auto era and shows the corresponding spread.

The second point is that there is another option for increasing the rate of change for the type of built stock. Pay for it. Set up tax/price systems that penalize over-sized distant building/living and reward smaller, more walkable building/living arrangements. Of course, this goes against TAD (the American Dream), so it cannot happen. And in any case it probably would only raise the replacement rate marginally (in reality, replacement of the building stock is just that, requiring the destruction of what is currently there...which takes money and time). Still, it's theoretically possible.