Slate columnist Matt Yglesias posted an important article yesterday, “In defence of the sun belt“, that should be required reading for all politicians and policy makers who’re interested in making Australian cities better. It reinforces how important it is to find ways to increase the supply of housing within our cities, especially in sought-after established areas.

He asks a straightforward question: why have US sun-belt cities such as Phoenix, Dallas, Houston and Raleigh-Durham grown so much faster than old, established places such as San Francisco and Boston, notwithstanding the considerable advantages of the latter?

Yglesias is a progressive, so he’s not really defending the sprawl characteristic of fast-growing cities such as Las Vegas. Rather, he’s asking why so many American businesses and workers are heading for new cities instead of old cities where the fundamentals are much stronger:

“That’s in terms of wages, it’s in terms of the basic first mover advantage that older cities have, it’s in terms of legacy cultural and entertainment amenities, and it’s certainly in terms of the things that urbanists say make for great communities.”

Why would businesses and people forego these advantages? And why, he wonders, would the old cities themselves, which have already “gone through the trouble of building the Metro and the street grid”, be prepared to settle “for a small tax base, a lack of job opportunities and a dearth of affordable housing”?

Many theories have been offered to explain the growth of sun-belt cities. The list of possibilities includes a warm climate, weak environmental regulation, low unionisation, cheap air travel, cheap air-conditioning, low taxes, sympathetic geography, public subsidies and the conquest of tropical diseases. There are also “push factors” associated with the older cities, such as poor public schools, antipathy to apartment living, unsafe neighbourhoods, cold climate and a higher cost of living.

However, Yglesias says the key reason is sun-belt cities actually want to attract business and population, so they make it easy to build infrastructure and housing. Land is cheap and building houses is cheap.

The older established cities, on the other hand, throttle housing supply, making it very expensive. As Edward Glaeser and Ryan Avent argue, residents of established areas employ a host of devices, including building controls, height controls and heritage controls, to deter increases in residential density.

He observes that the sun-belt model is doing something right — it’s clearly working for middle-class Americans. The new residents are getting houses that are large by any measure, as well as neighbourhoods they feel are safe and schools they think are good. In the sun-belt cities:

“Public officials and thought-leaders down to grassroots people in the community take a kind of pride in growth that leads you to sit down and say we want to work this out so that lots of houses and infrastructure get built here … (OTOH) Washington DC and its environs are absurdly squandering the fact that there’s high demand to locate things in and around our city. I don’t think that’s a point that’s best emphasised by highlighting the aesthetic failings of cookie cutter sun-belt subdivisions.”

There are real and potential weaknesses in the sun-belt model. Some argue their characteristically sprawled settlement pattern is vulnerable to big increases in oil prices. Others that they’re built on cheap water and electricity that is vulnerable to the exigencies of climate change. Nor is it likely sprawl in Dallas is as sustainable as absorbing the same growth within older, established cities such as San Francisco.