Migration into the human breeding population of Ann Arbor, Michigan, 1900-1950.

TN 1950 Lee E. Dice of the University of Michigan initiated a Study of assortative mating in the Ann Arbor community, which Study was supported by a grant from an anonymous donor. The principal objectives of the Study were to determine (a) whether people with similar traits tend to marry one another to a greater or lesser extent than would be expected by chance, (b) whether "similar" couples tend to produce more or fewer children than do "dissimilar" couples, and (c) what the effects of assortative mating and differential fertility might be on the genetic make-up of the population. Before these major objectives could be undertaken, however, attention had to be given to the problem of migration, for this phenomenon must be considered in any analysis of genetic variability in human populations. Unfortunately, most of the previous studies of internal migration in the United States have not been very useful for purposes of genetic study. This is because movement has been classified as "migration " and " notmigration " according to whether or not it was across a political boundary, such as a state or county line. The result is that the frequent cases of movement over short distances are not represented in the statistics on migration. For our purposes it was necessary to study the rate of migration into the Ann Arbor population in a way which would not be subject to the above mentioned limitations, and we did this by defining movement of any magnitude as migration, regardless of the political boundaries that may or may not be involved. Since the statistics which we have gathered are new and since they seem to lend themselves better to genetic interpretation than do most of those which have hitherto been published, we have seen fit to present them here.