Internal migration studies that examine the fertility impact of rural-urban migration have found support for the convergence of migrants’fertility rates to those of natives. Studies on internal migration in developing countries include Myers and Morris (1966) on Puerto Rico, Goldstein (1973) on Thailand, Martine (1975) on Colombia, Park and Park (1976) on Costa Rica, Hiday (1978) on the Philippines, Faber and Lee (1984) on Korea, Hervitz (1985) on Brazil, Lee and Pol (1993) on Mexico, Brockero¤ (1995) on thirteen African countries, Umezaki and Ohtsuka (1998) on Papua New Guinea and Kulu (2003) on Estonia. Convergence results are also obtained in studies of international migration, including Stephen and Bean (1992) and Lindstrom and Giorguli Saucedo (2002) for women of Mexican origin living in the US.

Convergence of migrants’ fertility rates might be due to selection rather than adaptation. Migrants do not constitute a random sample of the home population and they might exhibit lower fertility rates than the overall population. The studies described above do not control for potential selection e¤ects, with some ...nding that selection e¤ects played an important role in explaining the change in fertility associated with migration, while others did not or found that the presence or absence of selection e¤ects depends on the type of migration examined. Studies by Goldstein (1973), Hervitz (1985) and Kulu (2003) examined the various hypotheses and found strong support for the adaptation rather than the selection hypothesis, though White et al.’s (1995) found limited support for the latter in a study on internal migrants in Peru.<sup>2</sup> The impact of migration on the fertility of households back home has also been analyzed, though by a much smaller number of studies. One hypothesis examined is that the in‡uence of host countries’fertility norms persists after migrants return home and thus results in a decrease in fertility. For instance, Lindstrom and Giorguli Saucedo (2002) ...nd that Mexico-US temporary migration of women reduces longterm household fertility. Another hypothesis is that migration reduces fertility while the migrant is away and raises it when the migrant returns, a hypothesis con...rmed in the case of male migration (e.g., Hervitz 1985). The results have been interpreted as being due to interruption and catching up of fertility, with no clear long-term fertility impact.

Lindstrom and Muñoz-Franco (2005) examine the impact of migration on women’s — — modern contraceptive knowledge and use and thus on their fertility in rural Guatemala. They ...nd that contraceptive use increases and fertility falls with variables such as having family members in urban or international destinations, living in a community where urban migration is common, having social ties to urban or international migrants, and having an urban migration experience. They also ...nd that these variables become non-signi...cant once they control for their knowledge-di¤usion impact, concluding that it is through the knowledge acquired from urban migration experiences, contacts with urban or international migrants, or living in a community where such migration is prevalent, that contraceptive knowledge and use increases 2They ...nd that education and having fewer children are positively related to geographic mobility.

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