The PLVI is the street intersection around which front-foot land values average highest. Variety stores are common in the vicinity, as are banks. Firey also called attention to an interesting similarity between the edge of the central business district (CBD) and the "rurban" (rural-urban) fringe which often surrounds a city. Geographers, sociologists, economists, planners, and others have made studies, purportedly of CBDs, and have attempted in varying degrees to generalize from their results. One obvious direction for the Murphy and Vance inquiry was to find out what delimitation methods were in use or had been used in various cities by official agencies. Factories, apartment houses, and other non-central business uses may rank with office buildings and department stores in terms of height. So building heights obviously have decided limitations in attempts to approximate CBD boundaries. The chief possible value might be for a preliminary rough spotting of the boundary on the principal streets leading away from the city center.