# **1 Introduction**

Migration has become an increasingly politicized issue, in particular given the rise in unauthorized migration, igniting public and policy interest in its impacts and sparking new debates on the relationship between migration and economic development. Not surprisingly, the focus of the academic literature on unauthorized migration has been on the impact of irregularity on the host country. However, little is known about the consequences of irregular migration on sending countries. Studying the impact of illegality on the origin country is particularly important since unauthorized migration is often temporary, and many irregular migrants return to their home country either because they are deported or because they planned on temporary migration all along.

Return migration is an important phenomenon in the broad picture of international mobility. Although statistics on return migration are not reliable, recent estimates are that roughly one-quarter of all migration events are returns (Azose & Raftery, 2019). According to the OECD (2018), the five countries that experienced the largest outflows of foreign populations in 2016 were Germany (1.09 million), the Republic of Korea (325,000), Spain (243,000), Japan (234,000), and the United Kingdom (195,000). At the same time, irregular migration has been on the rise. According to the European Commission, every year, between 400,000 and 500,000 foreign nationals are ordered to leave the European Union because they have either entered or stayed irregularly in the destination country.

Irregular migration is not only an issue for OECD countries, but is also a challenge for the Gulf states and middle income countries like Malaysia and Thailand. For example, the United Nations Office for Drugs and Crime (UNODC) estimates that every year more than 660,000 people migrate irregularly to Thailand (Schloenhardt, 2014). Another example is Mexico, known for being a major migrant sending country to the United States, for its unauthorized emigration, and for its substantial return migration flows. According to the Mexican National Survey of Demographic Dynamics (ENADID), between 2009 and 2014, about half (48%) of the Mexican immigrant population in the United States was unauthorized, and one million Mexicans returned from the United States, leaving of their own accord (Gonzalez-Barrera, 2015).<sup>1</sup> Many other developing countries are likewise experiencing high return migration rates, as well as an increase in unauthorized emigration.

This paper is the first to examine the impact of undocumented migration status on migrants upon return to their home country. It investigates an unexplored question, namely the impact of the legal status of migrants on their wages upon return. We study the impact of return migration on wages by disentangling the effects of overseas legal versus illegal status and ask whether undocumented temporary migration has any impact on human capital accumulation that persists after return. From a conceptual

> 1 See Massey and Singer (1995) for an estimation of the probability of border apprehension and undocumented Mexican migration in the United States between 1965 and 1989.

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