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Many research and policy questions surrounding migration are causal questions. What causes people to migrate What are the consequences of migration for the migrants, their families, and their communities Answering these questions requires dealing with the self-selection inherent in migration choices. Field and natural experiments offer methodological approaches that enable answering these causal questions. This paper discusses the key conceptual and logistical issues that face applied researchers when applying these methods to the study of migration, as well as providing guidance for practitioners and policymakers in assessing the credibility of causal claims. For randomized experiments, this includes providing a framework for thinking through what can be randomized; discussing key measurement and design issues that arise from issues such as migration being a rare event, and in measuring welfare changes when people change locations; as well as discussing ethical issues that can arise. The paper then outlines what makes for a good natural experiment in the context of migration, and discusses the implications of recent econometric work for the use of difference-indifferences, instrumental variables (and especially shift-share instruments), and regression discontinuity methods in migration research. A key lesson from this recent work is that it is not meaningful to talk about “the” impact of migration, but rather impacts are likely to be heterogeneous, affecting both the validity and interpretation of causal estimates.

International migration offers individuals and their families the potential to experience immediate and large gains in their incomes, and offers a large number of other positive benefits to the sending communities and countries. However, there are also concerns about potential costs of migration, including concerns about trafficking and human rights, a desire for remittances to be used more effectively, and concerns about externalities from skilled workers being lost. As a result there is increasing interest in policies which can enhance the development benefits of international migration and mitigate these potential costs. We provide a critical review of recent research on the effectiveness of these policies at three stages of the migration process: pre-departure, during migration, and directed towards possible return. The existing evidence base suggests some areas of policy success: bilateral migration agreements for countries whose workers have few other migration options, developing new savings and remittance products that allow migrants more control over how their money is used, and some efforts to provide financial education to migrants and their families. Suggestive evidence together with theory offers support for a number of other policies, such as lowering the cost of remittances, reducing passport costs, offering dual citizenship, and removing exit barriers to migration. Research offers reasons to be cautious about some policies such as enforcing strong rights for migrants like high minimum wages. Nevertheless, we find the evidence base to be weak for many policies, with no reliable research on the impact of most return migration programs, nor for whether countries should be trying to induce communal remitting through matching funds.

The decision of whether or not to migrate has far-reaching consequences for the lives of individuals and their families. But the very nature of this choice makes identifying the impacts of migration difficult, since it is hard to measure a credible counterfactual of what the person and their household would have been doing had migration not occurred. Migration experiments provide a clear and credible way for identifying this counterfactual, and thereby allowing causal estimation of the impacts of migration. We provide an overview and critical review of the three strands of this approach: policy experiments, natural experiments, and researcher-led field experiments. The purpose is to introduce readers to the need for this approach, give examples of where it has been applied in practice, and draw out lessons for future work in this area.

A basic theoretical result is that if there is a Pareto-efficient allocation of risk across individual entities (in this case, individual household members) in a risk-sharing arrangement, individual consumption should not be affected by idiosyncratic income shocks. Data and Sample Construction The empirical analysis uses data from linked household surveys conducted by the Philippine National Statistics Office covering a nationally representative household sample: the Labor Force Survey, the Survey on Overseas Filipinos, the Family Income and Expenditure Survey, and the Annual Poverty Indicators Survey. The variables included in the vector of controls, Wh, are a set of household characteristics in the first period (January June 1997): an indicator for urban location; five indicators for the household head's highest level of education completed (elementary, some high school, high school, some college, and college or more; less than elementary omitted); six indicators for head's occupation ( professional, clerical, service, production, other, not working; agricultural omitted); and log per capita household For example, a need to accumulate resources for a large household purchase (such as a vehicle) or some other lump-sum payment (tuition, medical expenses) might lead to both increased remittances, increased domestic labor supply, and increased domestic income. Table 4 presents the results from OLS and instrumental variable regressions where the outcome variable is the change in household expenditures between the January June 1997 and April September 1998 reporting periods, expressed as a share of initial (January June 1997) household expenditures. This may reflect the fact that international migration requires fixed up-front costs (such as fees to recruitment agencies), so that households facing credit and savings constraints become more willing or able to pay the fixed costs when current income increases. Impact of Domestic Income Shock on All Outcomes, 1997 98: Fixed Effect OLS and Instrumental Variable Estimates, Controlling for Exchange Rate Shock, Migrant Households Only Migrant households Ordinary least squares 20.080* (0.042) 0.500*** (0.071) 20.032 (0.021) Instrumental variable 20.639** (0.219) 0.256 (0.169) 20.107 (0.176) Outcome Total remittance Total expenditure Overseas worker indicator Number of observations 1,655 1,655 *Significant at 10 percent level; **Significant at 5 percent level A key question is whether remittance responses to income shocks depend on the performance or availability of alternative methods of coping with risk, such as asset sales, credit markets, and reciprocal transfer networks. One reason for the finding of such large responses of remittances to rainfall-driven income shocks could be that such shared shocks make it more difficult to access credit or interhousehold assistance networks that normally help households cope with risk. Policies to facilitate remittances include strengthening financial infrastructure and payment systems to lower the cost and broaden the reach of formal remittance channels.