Urbanization 10,000+, 20,000+, 25,000+, 50,000+, 100,000+ / Per Capita

"Cities of 50,000 and over" includes "cities of 100,000 and over", "cities of 25,000 and over" includes "cities of 50,000 and over" in addition to "cities of 100,000 and over", and so forth.  The per capita data is for the same classes of cities.

The inclusion of data for cities of 20,000 and over as well as for cities of 25,000 and over was originally mandated by a lack of uniformity in reporting categories in the sources utilized. Since preparation of the original version of the file, however, a series of missing data estimates, proportionally calculated across urbanization categories, have been prepared. The procedure for calculating these entries is discussed in Banks and Carr, op. cit.

In assembling the urbanization data, considerable difficulty was encountered with regard to the definition of "city" or "urban area". Insofar as possible, data for core cities or urban areas are employed, excluding greater metropolitan or suburban populations. In cases where the reference units are not adequately defined, every effort has been made to cross-check the relevant figures against those reported in other sources. It cannot be claimed, however, that the reliability problem is completely surmounted, particularly for recent years, when deliberate redefinition by reporting agencies has tended to yield longitudinal discontinuities.