14 an important area for further inquiry.<sup>28,29</sup> More research is also needed to better understand the costs<sup>30</sup> and benefits to internal migrants (including return migrants), and the role of social networks and secondary towns.<sup>31</sup> When discussing labor mobility, it is also important to consider the gender dimension that affects migration decisions and outcomes. This holds for voluntary migration, as discussed above, but even more so for forced migration (World Bank, 2017a). Forced displacement can transform gender norms. It may create opportunities for education and access to employment opportunities, as for rural Afghan women who are refugees in the Islamic Republic of Iran (Monsutti, 2006). Women’s skills may also be better transferable than men’s, enabling them to find work more easily, for example as domestic workers (Buscher, 2009). Yet, women and girls are also at greater risk of physical violence (rape, sexual abuse) during the flight and at destination, also within the household, with displaced Afghan women reporting domestic abuse happening more frequently during displacement than before (JIPS, 2012a).

**Local Job Opportunities.** The negative social externalities in origin regions associated with migration are likely to be more than compensated by the benefits resulting from reduced unemployment, poverty reduction (when the migrants themselves are poor) and, indirectly, through remittances, diaspora investments, skill and technology transfer and increased trade and foreign direct investment (FDI).  Remittances (international and internal) are an important way of sharing prosperity between different places and the importance of international remittances (more than three times the size of official development assistance) and their contribution to development has attracted a great deal of attention over the past 10-15 years.

28 Bryan, Chowdhury and Mobarak (2014) show how a small travel grant or credit (randomly distributed) to poor rural laborers in Bangladesh (conditional on seasonal migration) can induce recipients to move to towns and cities for temporary work during the agricultural low season. While indicative of market failures, at the same time, uptake remains moderate (one-fifth of the recipients) (Hicks et al., 2017). The experiment is now replicated and evaluated at a larger scale (https://www.evidenceaction.org/thesolution-no-lean-season/).

29 In a more dynamic perspective, spatial inequality often forms a fertile breeding ground for conflict, especially when it coincides with differences in ethnicity, religion or language (Langer and Stewart, 2015). Conflict in turn reinforces the migratory pressures from spatial inequality.

30 As with international migration, rural-urban transport costs are often only a fraction of the annual income gain that could be obtained from moving (Christiaensen, De Weerdt and Kanbur, 2017). Schwartz (1973) emphasized this early on, showing that the adverse effect of distance on migration follows especially from diminishing-information (i.e. rising jobs search costs), and less likely from actual transport (or even psychic costs).

31 Migration costs typically increase with distance, and thus also the likelihood that liquidity and credit constraints bind. This is one of the reasons why secondary towns may attract more rural migrants, than cities, even though the potential income gains are larger in the latter. Migration costs can be also partly overcome through social networks, by reducing the monetary and informational constraints as well as the psychological costs (Seshan, 2017). This explains the important role of migration networks in understanding migration flows and the choice of destination. Yet, the likelihood of these networks establishing is itself a function of the distance to the destination and the existence of market failures, reinforcing the role of secondary towns in mediating migration (Ingelaere et al., 2017). Alternatives to facilitating labor mobility to close the income gap (and avoid negative externalities from migration flows and stocks) are to increase the livelihood prospects in the location of origin, including through foreign aid, trade and capital mobility as well as fostering return migration. Indications are that moving also “pays” in times of conflict, with those leaving tending to suffer less (physically and economically) than those who stayed behind (Etang Ndip, Hoogeveen and Lendorfer, 2015: World Bank, 2017a). But the poorest often do not have the means or social connections to leave.