International Migration

In 2020, an estimated 281 million people lived outside their country of birth, representing a 62% increase from 173 million in 2000 (United Nations 2020). When moving from developing to developed countries, workers routinely experience wage increases of four- to fivefold or greater upon migration, and in some migration corridors the gains exceed 1000% (Clemens et al. 2019). These gains are larger than those demonstrated in any in situ development intervention (Pritchett and Hani 2020). There are “trillion-dollar bills on the sidewalk” waiting to be picked up through the liberalisation of international labour mobility (Clemens 2011).

Funded by their increased incomes, migrants send substantial funds back to their home countries. Migrant remittances have grown from US$71 billion in 2000 to US$656 billion in 2023, making them one of the largest types of international financial flows to developing countries (Vandana et al. 2023). These flows are more than double official development assistance, and in recent years have surpassed foreign direct investment flows.

Nearly all developing country governments have incorporated international migration into their development policymaking. United Nations (2019) finds that 94% of developing countries with populations over one million have a dedicated government agency implementing migration policy, 88% have agencies focused on overseas employment or diaspora engagement, and 78% have policies promoting migrant remittances. Many policymakers in developing countries view migration not as a problem to be contained, but an opportunity to be harnessed for development. International financial institutions also recognise that migration policy is a key component of national development policy (World Bank 2023).

This VoxDevLit synthesises the literature on international migration and its impacts on origin countries. We emphasise studies that use research designs that can credibly establish causal relationships, in keeping with prior surveys (Yang 2011, McKenzie and Yang 2024, Batista et al. 2025a). We focus exclusively on international migration from developing to developed countries. We do not address effects on destination populations, on which there is an extensive separate literature (National Academies of Sciences, Engineering, and Medicine 2017). Almost all the studies we review are on ‘economic migrants’ who travel in search of employment opportunities, not education, marriage, or other purposes. As such, the literature on forced displacement and refugee populations is also largely out of scope for this review.[1]1. Recent reviews of forced migration in economics include the VoxDevLit of Rozo and Grossman (2025), Ruiz and Vargas-Silva (2013), Maystadt et al. (2019), and Verme and Schuettler (2021).

The review is organised into seven sections. Section 2 documents how migration helps the migrants themselves. Section 3 examines impacts on migrant families left behind. Section 4 examines how migration affects origin areas. Section 5 discusses the ‘brain drain’ versus ‘brain gain’ debate. Section 6 reviews other effects on origin areas, on foreign direct investment and trade linkages, innovation and knowledge transfers, and changes in political and social norms. Finally, Section 7 discusses migration policies to promote development. Throughout, we discuss potential future research directions.

For full reference list see the end of the conclusion chapter.