Empirical research on US immigrants is reviewed: their productivity an
d assimilation; their contribution and use of public services; and the
ir impact on native Americans. I discuss the characteristics of cohort
s of immigrants that enter the United States at different times, and t
hen quantify the assimilation of immigrants, typically in terms of eco
nomic productivity of immigrants compared with natives. Few have found
quantifiable negative effects of immigrants on native wages or unempl
oyment in local labor markets, but a more general equilibrium approach
than has been empirically implemented may be needed to draw any concl
usions regarding the distributional consequences of immigration.