The study we did for the City of Idaho Falls -- which must have been roughly 1988–89 -- did not use zoning at all. It was based on actual use, as checked in the field and measured on aerial photos. We did not attempt to relate land use to employment. We asked around and found out that the City of Grand Island, NE, which was very similar to IF in both population and economic function (as a regional trade center) had just done a similar study. I can't keep numbers in my head over that many years, but I do recall being surprised. It probably, at least in part, had to do with jurisdictional boundaries, i.e. which city had annexed more of the city edge type industrial uses. I do not think there would be that much variability if you isolated retail and office uses, but the particular history of different cities has a profound influence on the space uses consume. Neither IF or GI has a particularly healthy CBD, for example, so I suspect retail consumes vast acreages in such cities as compared with places that have healthy downtowns. I also am reasonably sure that industry expands to fill the space it can afford, so that the relatively affordable land in rural trade centers probably leads to more space devoted to industry than it would where land is more valuable. This is all based on informed intuition, of course, not on extensive research.
