"This paper examines the impact of a college or military installation in a [U.S.] metropolitan area on the age structure of the migration for the area. We find that the presence of such institutions causes significant and systematic impacts on age patterns of in- and out-migration that may not be obvious a priori. Failure to account for these effects in studies of gross migration (whether or not aggregated over age groups), or of net migration by age, will typically lead to bias or to inefficiency in the results, depending on the techniques of analysis used." excerpt