The Census Bureau has released a new report (pdf) comparing the growth of Metropolitan Statistical Area central and outlying counties between 2000 and 2007.
Wendell Cox says the report shows "that the nation continues to suburbanize, despite the consistent media 'spin' that people are leaving the suburbs to move to core cities."
[T]he conclusion of the new report is clear. The nation’s most remote suburbs – its exurbs – are growing much faster than the central counties. Whether this trend will now reverse, of course, is up to debate. Perhaps demographic changes and higher energy costs will slow expansion on the outer fringes. More likely, the current recession may well lead to less exurban growth, but history suggests this may prove only a short-lived trend.
My own take is that this report offers little meaningful information other than growth and migration rates for the MSAs as a whole. Breaking out the numbers for central counties and outlying counties tells us little because the Bureau defines "central counties" expansively as those containing all or a substantial portion of the MSA's urbanized area. Since a city's urbanized area can and often does stretch across several counties, the Bureau's definition sweeps up counties that we typically consider suburban. For example, Travis and Williamson are "central counties" in the Austin-Round Rock MSA, even though Williamson is the quintessential suburban county. (Hays is considered an outlying county, but will almost certainly be a central county in the next census due to the rapid spread of Austin's urbanized area.)
Because of the broad definition of "central" counties, almost all MSA population is "concentrated" in these counties. In MSAs with more than 5 million, for example, 97.4% of the population lived in central counties (2007 estimates). For all MSAs, the number is 91.8%.
Naturally, because central counties began with a large baseline population, even large absolute increases in population yielded smaller percentage increases than small absolute increases in the less populous exurbs. For example, in the Midwestern MSAs, the outlying counties grew at nearly twice the rate of the central counties. But the central counties added 5 times as many people. The New York-Northern New Jersey-Long Island MSA is an even more extreme example. Its central counties grew by 2.6% between 2000 and 2007 while its outlying counties grew at an explosive 26.6% rate. But the central counties added 480,000 people to just 12,000 for the outlying counties, 40 times as many.
For the United States as a whole, MSA central counties added nearly 17 million people compared to 2.4 million for outlying counites. Central counties in the northeastern region (which includes New York) added nearly 1 million while the outlying counties added fewer than 24,000. The South Region's outyling regions added the most by far -- nearly 1.8 million -- but even here the outlying growth was dwarfed by the 7.7 million added by the central counties.
If the Bureau's goal was to tell us something important about the relative growth of exurbs and central cities, it failed. There's just not much to the data because of the overly-expansive definition of central counties. As Wendell points out, this report might very well understate suburban growth (in fact, this is almost certainly true), but this report doesn't shed much light on the question. Wendell himself recognized this limitation on the data, but unreasonably, I think, attempted to draw an unwarranted conclusions from the report anyway.