This paper examines the bias arising from individuals' migration from administrative outcome data, with a focus on the labor market consequences of postsecondary education. We find that out-of-state migration is particularly problematic for high-earners, flagship graduates, and certain majors. Consequently, the effect of graduating from a flagship university is 10% higher than one would estimate using in-state earnings exclusively, though the extent of bias differs substantially across contexts. The impact of obtaining a 2-year CTE credential is also understated, as are earnings differences across majors. Approaches to testing for and bounding this bias are considered.