Paper of the Day

I’ve previously linked to research showing that while it’s not clear that sprawl leads to obesity, it does seem to be the case that the obese opt to live in sprawl, such that there is a correlation between the two. Here‘s something more on the connection:

In this paper, we examine the effect of changes in population density—urban sprawl—between 1970 and 2000 on BMI and obesity of residents in metropolitan areas in the US. We address the possible endogeneity of population density by using a two-step instrumental variables approach. We exploit the plausibly exogenous variation in population density caused by the expansion of the U.S. Interstate Highway System, which largely followed the original 1947 plan for the Interstate Highway System. We find a negative association between population density and obesity and estimates are robust across a wide range of specifications. Estimates indicate that if the average metropolitan area had not experienced the decline in the proportion of population living in dense areas over the last 30 years, the rate of obesity would have been reduced by approximately 13%.

Another datapoint, at least.

Comments

  1. Karl Smith says:

    Clever.

    I am reading through now and thinking about confounding issues – white flight, income ratios, etc.

    What I can’t see them controling for right off is whether or not obese people, whatever their orgin, are more likely to move to metros in which their is sprawl.

    So for example suppose the design of the system meant their was less opportunity for sprawl in the Northwest. As a result fewer obese people moved to the Northwest.

    How do we decouple that effect from the sprawl causing people to be obese.

    That is, highways can be an instrument if we are thinking about the obese moving between the central city and the suburbs of a given metro, but how can they control between metros.

    This may be addressed.