Objective. We seek to measure stocks of migration-specific human and social
capital available to Mexican immigrants and to quantify their effect in pr
omoting out-migration to the United States. Methods. We use data from the M
exican Migration project to measure the share of people in western Mexico w
ho have been to the U.S., who are socially connected to someone who has mig
rated to the U.S. in the past, and who are socially connected to someone li
ving in the U.S. at the time of the survey. Results. We find that 40% of ho
usehold heads from this region-and 20% of all persons of labor force age-ha
ve been to the United States at least once in their lives. In addition, 25%
of household heads have an immediate family member currently living in the
United States; 61% have a member of their extended family living north of
the border; and 37% report knowing a friend in the U.S, at the time of the
survey. All told, 73% of household heads in western Mexico are socially con
nected to someone living north of the border, and 81% at least know someone
with U.S. experience. Conclusions. These extensive stocks of human and soc
ial capital lead to very high probabilities of out-migration over the cours
e of a Mexican's life and suggest that migration to the United States may c
ontinue even as economic pressures to migrate diminish.