Monthly Archives: August 2013
Mr. Zakaria engages in over-reach with respect to the Harvard-Berkeley study. He is not the first. The Harvard-Berkeley study was not about urban form, cities or segregation. It was about the relationship between income mobility and tax expenditures.
The authors provided additional information with 25 separate, simple correlation analyses between 25 individual variables and economic mobility (demographic factors were not controlled). Co-Author Raj Chetty described this supplemental research in a PBS interview, citing income segregation, school quality, two-parent families and measures, civic engagement, religiosity and community cohesiveness. The authors urged caution in interpreting these correlations: “For instance, areas with high rates of segregation may also have other differences that could be the root cause driving the differences in children’s outcomes.”
Columnists and some analysts have taken simple correlation analyses
— which does not control for other factors (not even the other 24 that were calculated) — to make their urban form points. In contrast, perhaps the most rational voice was Columbia University urban planning professor David King, who noted that: “…snapshot correlations really don’t mean anything and will provide evidence for whatever point of view is desired.”
Simple correlation analysis is not enough. There is a need to control for other important factors. That’s why we have econometric analysis.
This issue is discussed in greater detail in “Distortions and Reality about Income Mobility” at http://goo.gl/xSM6v7
Actually the claim that 1,000,000 baby boomers moved to within 5 miles of downtown in the 50 largest cities between 2000 and 2010 is patently false. Census Bureau data shows that there was a 66,000 loss in population within 5 miles of the city halls of the 51 metropolitan areas over 1,000,000 population. See: “Flocking Elsewhere: The Downtown Growth Story,” http://www.newgeography.com/content/003108-flocking-elsewhere-the-downtown-growth-story.
There is no way a net 1,000,000 baby boomers could have moved so close to downtown, and the data shows it. The actual census data on baby boomers shows a loss of more than 1 million boomers inside the core cities, which largely include this 5 mile radius.
The authoritative source for such data is the United States Census Bureau (which is the source of the data referenced here).
Also see: Similar Wall Street Journal Error
Between 2000 and 2010, there was a loss of 66,000 residents, of all ages, within a 5 mile radius of the cores of the 51 largest cities (metropolitan areas) in the nation. It could therefore not be that “more than a million baby boomers moved to within 5 miles of the downtown of the 50 largest cities between 2000 and 2010” (unless, of course virtually the same number moved out). For a summary of the trend as reported in US Census data, see “Flocking Elsewhere: The Downtown Growth Story,” at http://www.newgeography.com/content/003108-flocking-elsewhere-the-downtown-growth-story.