“America’s Truly Densest Metros

• RICHARD FLORIDA
• OCT 15, 2012

Economists and urbanists have long argued that density plays a key role in innovation and economic growth. As important as it is, density is a tough thing to measure. Metros come in different shapes as well as sizes: Some have more concentrated populations near the center, others are more continuously sprawling. Yet, density is typically measured rather crudely by simply dividing the total population of a city or metro area by its land area.

A new report [PDF] from the U.S. Census Bureau helps to fill the gap, providing detailed estimates of different types of density for America’s metros. This includes new data on “population-weighted density” as well as of density at various distances from the city center. Population-weighted density, which essentially measures the actual concentration of people within a metro, is an important improvement on the standard measure of density. For this reason, I like to think of it as a measure of concentrated density. The Census calculates population-weighted density based on the average densities of the separate census tracts that make up a metro.

The differences in the two density measures are striking. The overall density across all 366 U.S. metro areas is 283 people per square mile. Concentrated or population-weighted density for all metros is over 20 times higher, at 6,321 people per square mile.

This Census report is not the first to use population-weighted density. A 2001 study by Gary Barnes of the University of Minnesota developed such a measure to examine sprawl and commuting patterns. In 2008, Jordan Rappaport of the Kansas City Fed published an intriguing study in the Journal of Urban Economics (non-gated version here), which looked at the relationship between density (including population-weighted density) and the productivity of regions. Christopher Bradford, who blogs at his Austin Contrarian, has also advocated for using population-weighted density to better understand urban development.

What’s particularly useful about the new Census report is that it provides detailed data on population-weighted density for all U.S. metros for both 2000 and 2010 (full data set here [xls]). This took some doing, because metro boundaries change over time. To develop consistent estimates, Census researchers went back and recalculated population-weighted densities for 2000 based on the revised metro boundaries for 2010. This makes it possible to compare the two time periods and examine changes over time.”