We feel compelled to clarify some of the ambiguities created by Harold Henderson’s critique of Jane Holtz Kay’s Asphalt Nation (February 20, 1998). The Center for Neighborhood Technology was cited as Kay’s source for inaccurate data pertaining to the amount of land consumed between 1970 and 1990. There has been a great deal of debate over what the proper figure for land consumed is, and Mr. Henderson has been privy to much of that debate. Check in your files for our November 12, 1996, letter to the director of information services of the Chicago Area Transportation Study; Mr. Henderson was copied on that letter, which sets out in some detail (eight pages worth of detail!) the problems with citing any particular figure.
In essence there are multiple reasons why two different figures are cited for the amount of land consumed during that 20-year period. Sometimes the increase in residential land, as estimated by the Northeastern Illinois Planning Commission, is cited; sometimes the total increase (including increases in commercial and industrial land) is used. The second is obviously a much larger figure (an additional complication is that streets, utilities, and a few other land-use categories that have experienced growth concomitant with overall growth are not included in all the estimates). Additionally, the Northeastern Illinois Planning Commission released one set of estimates in 1992 and then released a new set of estimates later. The 1992 figures had already become part of published analyses on land use and transportation infrastructure.
What this very brief overview points to is the complexity of making these estimates–and they are just estimates. The case for why one set of numbers is superior to another is actually much more complicated than this and of interest mainly to demographers and statisticians. Reasonable people can reasonably disagree about which methodology produces the most accurate result. A disservice is being done the public by the implication that all of these policy questions have simple yes or no answers, based on only one credible set of data. The world is much more complicated than that. Lost in the obfuscation over data types is the fact that the region spread out much faster than population grew, whether that number was the variously quoted 35, 44, 46, 52, 55, or 65 percent figures. We can’t afford land consumption at any of those levels.