The significance of mobility and the use of persistence studies

Economists and historians have long been interested in the amount of geographic mobility in a society for a number of reasons. The extent of geographic mobility can indicate the degree to which labor will move in response to changing opportunities, and contribute to an efficient allocation of productive resources in an economy. The amount of geographic mobility is often considered a determinant of the political and social stability of a society. And the frequency with which the members of a population move can suggest the extent of economic opportunity in a community. Although in each of these cases the interpretation of mobility requires care, because the many causes and effects of individual migration make its linkages in the aggregate to each of these social and economic consequences varied and complex, the extent of geographic mobility has nonetheless been considered a basic characteristic of a society.

One common approach to the study of migration in American history has been the measurement of geographic persistence. Since the pioneering studies of migration in rural Kansas by James Malin, in Trempealeau County, Wisconsin, by Merle Curti, and in Newburyport, Massachusetts, by Stephan Thernstrom, a series of studies have been done that measure the persistence of a population in a particular location by calculating the proportion of a sample of individuals from a chosen base year that could still be found in that location at some subsequent date, typically 10 years later.