A literature review and fresh evidence are presented on economic motives for migration and barriers to moving. Given urban income opportunities, higher rural incomes are shown to deter decisions to move from countryside to town. Rural-urban migrants enjoy substantial gains on average, though selection into migration is estimated to be negative on unobserved traits and skills. Those who do not move forego substantial, potential gains. Ethnolinguistic minorities, those living at greater distances from cities, and the socially disadvantaged with lower levels of schooling forego the most. Thus, very real barriers to migrating arise for these populations, though it remains unclear to what extent the constraints are financial, discomfort with the prospects of urban life, or concern to be near kith and kin. However, the amount of potential gain to nonmigrants does not decline at higher income levels of countries, suggesting financial barriers may not be paramount.