Childhood obesity is a major public health problem both globally and in the United States (Institute of Medicine 2004; Troiano et al. 1995). At the same time, extensive immigration to the United States, Canada, Europe, Australia, and New Zealand (NZ) has led to large increases in the number of foreign-born children in these countries, with many, if not most, of these children being born in developing or transition countries. Although economic migrants moving from a developing to a developed country will generally experience large gains in income and increased access to health care and clean water, this migration also potentially introduces unhealthy lifestyle patterns, such as increases in fat and refined sugar-rich diets and decreases in regular physical activity (Clemens, Montenegro, and Pritchett 2008; McKenzie, Gibson, and Stillman 2009; Popkin and Udry 1998). Thus, migration may potentially have negative impacts on health, particularly of still-growing children who are most affected by environmental and dietary changes. (1)
Child health is of intrinsic interest, both as a current measure of well-being and a source of future human capital. Moreover, given the strong economic argument for increasing international migration, it is important for economists to also examine other impacts that migration can have on well-being and whether these impacts lower the net benefit of migrating for individuals and for society as a whole. However, identifying the causal impact of migration on child health requires comparing the current health of migrant children to what their health would have been had they stayed in their home country. This counterfactual is typically unobserved, and thus the current literature settles for either comparing the health of immigrant children to that of native-born groups in the destination country (e.g., Bell and Parnell 1996; Frisbie, Cho, and Hummer 2001; Gordon et al. 2003; Institute of Medicine 1998; Kirchengast and Schober 2006) or comparing the health of immigrant children in the destination country to that of similar nonimmigrant children in the source country (e.g., Smith et al. 2003). Both of these approaches assume that there is no selectivity into migration and thus the health of nonmigrant children can be used as an appropriate counterfactual for what the health of migrant children would have been in the absence of migration. (2) These approaches are not very convincing because migrant families are likely to differ from nonmigrant families along a host of unobserved dimensions, some of which are likely to be correlated with both child health and migration.
This paper overcomes this problem by examining the impact of migration on children's health in the context of a unique survey of participants in a migrant lottery program. The Pacific Access Category (PAC) under NZ's immigration policy allows an annual quota of Tongans to migrate to NZ. The other options available for Tongans to migrate are fairly limited, unless they have close family members abroad. Many more applications are received than the quota allows, so a ballot is used by the NZ Department of Labour (DoL) to randomly select from among the registrations. The same survey instrument, designed by the authors, was applied in both Tonga and NZ and allows experimental estimates of the impact of migration on child health to be obtained by comparing the health of immigrant children whose parents were successful applicants in the ballot to the health of those children whose parents applied to migrate under the quota, but whose names were not drawn in the ballot. This survey instrument collected information on both parental-reported health and measured anthropometrics, as well as additional data on household income, diets, and access to health care facilities. Thus, we are able to examine whether migration has a causal impact on child health or whether migration just changes parents' reference points for what "good health" means, and examine the pathways through which changes in child health occur. …