Migration and marriage: Modeling the joint process

BACKGROUND Previous research on interrelations between migration and marriage has relied on overly simplistic assumptions about the structure of dependency between the two events. However, there is good reason to posit that each of the transitions has an impact on the likelihood of the other, and that unobserved common factors may affect both migration and marriage, leading to a distorted impression of the causal impact of one on the other. OBJECTIVE We will investigate the relationship between migration and marriage in the United States, using data from the National Longitudinal Survey of Youth 1979. We allow for interdependency between the two events and examine whether unobserved common factors affect the estimates of both migration and marriage. METHODS We estimate a multi-process model in which migration and marriage are considered simultaneously in regression analysis and there is allowance for correlation between disturbances; the latter feature accounts for possible endogeneity between shared unobserved determinants. The model also includes random effects for persons, exploiting the fact that many people experience both events multiple times throughout their lives. RESULTS Unobserved factors appear to significantly influence both migration and marriage, resulting in upward bias in estimates of the effects of each on the other when these shared common factors are not accounted for. Estimates from the multi-process model indicate that marriage significantly increases the hazard of migration, while migration does not affect the hazard of marriage. CONCLUSIONS Omitting interdependency between life course events can lead to a mistaken impression about the direct effects of certain features of each event on the other.