A second advantage is that Treasury employees, who have access to the underlying Social Security numbers for the individuals in our data, can identify individuals’“birth” states, that is, the states in which individuals had resided when they applied for their respective Social Security numbers. 9 The final sample contains 753,521 observations, covering 85,888 distinct taxpayers. This overall sample can be divided into natives, nonnatives, and others. Na- tives are individuals: (i) who reside in the same Metropolitan Statistical Area (MSA) over the sample period, and (ii) whose current state of residence is their birth state. 10 Nonnatives are individuals whose current MSA does not overlap with their birth state (., a.
