The American Community Survey (ACS) and the Annual Social and Economic Supplement (ASEC) of the Current Population Survey (CPS) both collect data on geographical mobility. In some cases, migration estimates are comparable. For instance, annual migration rates between the ACS and ASEC. In the case of 5-year ASEC migration estimates and 5-year multiyear ACS estimates, the estimates are not comparable under any circumstance. After describing the relevant history behind each set of estimates, this paper explains why they are not comparable, which one to use, and when.