Do you have to be tall and educated to be a migrant? Evidence from Spanish recruitment records, 1890-1950

We use Spanish military records stemming from the late-19th to the mid-20th century to assess internal migrants' self-selection. We find that migrants were, on average over the whole period, around one centimeter taller than non-migrants, and in the booming 1920s, the height advantage of movers reached three centimeters. The positive self-selection was larger for migrants originating in poorer provinces and traveling longer distances. A further finding is that migrants were positively selected in terms of literacy and socio-economic status according to their occupation. Professionals were most likely to have migrated internally and farmers least.