Confidence to be given findings derived from fixed-period definitions of migration

Some of the errors in measurement of migration and its determinants that occur with the use of fixed-period data are identified. Consideration of this issue yields a typology of studies based on the nature of the determinants related to migration. Sources of distortion are numerated. The logical severity of each distortion is detailed. Use of the typology permits an appraisal of the potential confidence to be given to the validity of findings associated with classes of migration research which use fixed-period data. A test case is examined to illustrate the usefulness of the typology.This research was supported in part by the NSF Grant No. SOC76-81767, for the study, "A Test of Competing Explanations for Migration Differentials." Funds for computer time and technical assistance were also provided by the Department of Sociology, The University of Tennessee, Knoxville.