The "College-Dense and Car-Light" Theory

"The members of the The Atlantic Business Channel (where Derek Thompson works as a senior editor) all live in New York City. At various points in our lives, we have all lived in Washington, D.C., too. And these two cities...happen to be the two metros with the highest share of non-car households in America, according to the University of Michigan’s Transportation Research Institute," writes Thompson.

When Thompson looked at the graph (located in the article) of the 30 cities showing which metros have the highest and lowest rates of "non-car households" (as well as the U.S. average), the first thing he thought of was not what the researcher told The Wall Street Journal:

The five cities with the highest proportions of households without a vehicle were all among the top five cities in a recent ranking of the quality of public transportation," said Michael Sivak, director of Sustainable Worldwide Transportation at Michigan.

"When I see New York, D.C., Boston, Philadelphia, San Francisco [the top-five, respectively, no-car households], the first thing I think is: These are all the classic, even cliche, magnets for elite college graduates," he wrote.

So I compared the cities' non-car ownership rates to their share of bachelor's-degree holders. And it turns out there is a statistically significant relationship between being college-dense and car-light. [Scroll across the interactive dot graph (under the aforementioned graph in article) that reveals "% no-car, % college"]

Thompson recognizes that "what we're looking at here is an underlying variable of city density. Highly productive cities that are magnets for talented (and rich) people tend to be crowded with twentysomethings trying to start their careers. Small crowded cities get clogged, and clogged cities require the kind of effective public transportation that makes cars an expensive nice-to-have rather than a have-to-have," he writes.

The theory doesn't appear to hold, though, for Austin and San Jose, the major city of Silicon Valley, ranked third-to-last and last, respectively, in the ranking of carless households.

Sivak's report, "Has Motorization in the U.S. Peaked? Part 4: Households without a Light-Duty Vehicle" [PDF] was discussed here and also in USA Today.