The economic performance of U.S. immigrants differs substantially from that
of natives in ways that pose difficulties for standard theories of migrati
on. In particular, immigrants cluster geographically and are often employed
together. Immigrant earnings differ by origin and time spent in the United
States, even after controlling for education and experience. A large fract
ion of immigrants eventually returns home, even to low-wage countries. This
article offers a theory of international migration based on assortative ma
tching under imperfect information that accounts for a broad range of these
empirical regularities.