Edward L. Glaeser responds:

While I appreciate the suggestion that I just make things up out of whole cloth, I regret to inform you that in this case, I used the U.S. Census, American Fact Finder.

The Census is the standard source for housing values in cities, not the National Association of Realtors (NAR), and there is a good reason for that. The NAR gives you the price of average sales during a particular (recent) time period. It does not give you the sales price for an average existing home in a region. Recent home sales are quite unrepresentative of the overall population of housing in a city. They tend to be newer and much more expensive. In an older city, the NAR data is extremely unrepresentative of the city as a whole. Few housing experts would actually use them to look at overall housing costs.

The Census data has its own problems. It represents a self-reported housing value, not a sales price. The research on problems with self-reports suggests that these self-reports tend to overstate actual housing prices, which suggests that the 61,000 figure overstates the true sales prices.