1 Harvey and Clark (1965). Harvey and Clark took the internal quotation from Pearson (1957).
2 The simple models are estimated with an eye towards facilitating comparisons and validating measures of urban form. They are best viewed as exploratory. See our companion paper, Malpezzi (2000) for a more detailed model, albeit with the estimation focused on a single measure.
3 Although McDonald, in his excellent (1989) review, suggests that Stewart (1947) apparently first fit the negative exponential form described here. Most observers would agree that it was Clark (1951) who popularized the form among modern urban scholars.
4 The world is also divided up into people who divide the world into two kinds of people, and people who don't, but that's another paper.
5 But see Wheaton (1977) and Glaeser et al. (2000) for dissenting views.
6 A larger set of scatterplots, and the key to the three-letter codes for MSAs in Figures 2 through 6, are available at http://wiscinfo.doit.wisc.edu/realestate/urban_indicators.htm
7 The matrix of correlations is also available at our website.
