Renn pointed me towards the work of Edward Glaeser, the Harvard economist and U. of C. grad who’s become one of the most prominent analysts of the American city in the 21st century. And he thinks there’s a strong correlation. He’s got a whole paper on it, in fact: “Smart Growth: Education, Skilled Workers, & the Future of Cold Weather Cities.”
Cities with average January temperatures under 30 degrees Fahrenheit grew in population only one-third as quickly from 1960 to 1990 as did cities with average January temperatures above 50 degrees. The shift of population toward the Sun Belt can also be seen at the state level: while population in the colder 25 states grew 95 percent between 1920 and 1980, the warmer 25 states saw their average population grow 309 percent…
In short, there’s something of a chicken-and-egg question with the air-conditioning solution that Glaeser cites. Adoption of air conditioning, across the South, was slower than you might expect from the weather. Its availability is a well-established boon to the South, but so is being able to power and afford air conditioning.
It’s significant that Enrico Moretti, like Glaeser an economist interested in how knowledge workers cluster in cities and regions, has most recently turned his focus back to the Tennessee Valley Authority. That’s a government project so ingrained in Southern culture that, as a kid, I thought that the Tennessee River was just called the TVA (emphasis mine):
We find that the TVA’s direct productivity effects were substantial. The investments in productive infrastructure resulted in a large increase in local manufacturing productivity, which in turn led to a 0.3% increase in national manufacturing productivity. By contrast, the indirect effects of the TVA on manufacturing productivity were limited. While we do find strong evidence of localized agglomeration economies in the manufacturing sector, our empirical analysis clearly points to a constant agglomeration elasticity. When the elasticity of agglomeration is the same everywhere in the country, spatially reallocating economic activity has no aggregate effects, as the benefits in the areas that gain activity are identical to the costs in areas that lose it. Thus, we estimate that the spillovers in the TVA region were fully offset by the losses in the rest of the country.
The intensely regressive economic (and cultural) practices of the South damned up potential across its old borders; once they began to fall, it created a flood, draining Yankee knowledge, technology, and workers.
While everyone wants to talk about the weather, it isn’t the only factor nor the most important factor in population and economic growth. To suggest this is the case is to rely on strong ecological arguments, perhaps like those made by Jared Diamond in his more popular books. Yes, air conditioning matters but humans were able to live in both the warmer South and colder North before air conditioning or central heating. More broadly, factors like electricity and water (see the recent troubles in the Southwest) matter more and are essential to even having air conditioning in the first place. Thus, the twist of invoking the TVA, an important adaptation to nature, makes the matter all the much more complex: essential infrastructure makes all sorts of other things possible.