# 1. Introduction

The world has undergone a remarkable transformation in recent decades through the economic development of low- and middle-income countries. The share of the extreme poor fell from 36.3 percent of the world population in 1990 to 8.63 percent in 2018, reducing the number of the poor by about 1.3 billion.<sup>1,2</sup> This progress has been a consequence of rapid and pro-poor growth in many low-income countries. Between 2000 and 2020, per capita incomes in countries that were in the bottom third in 2000 grew by 3.3 percent annually, compared to 1.4 percent for countries that were in the top third.<sup>3</sup> The relationship between economic development and migration has been of keen interest for researchers and policy makers alike. Poverty is commonly considered to be one of the “root causes” of migration. One of the early economic framings of the migration decision was to consider it as a costly investment to reap the earnings differentials across different locations (Sjaastad 1962). This suggests that a high prevalence of poverty, or lower incomes, would induce many to incur the cost of migration and move to higher-income countries. In this framing, the propensity to migrate would decline as low-income countries get wealthier as some people would now choose not to migrate. This simple, but somewhat naïve, concept has also permeated policy makers’ thinking about the link between migration and development.

Consequently, policy makers in some high-income destination countries are exploring how to use development policies and aid to curb (irregular) migration. For instance, the US Commission for the Study of International Migration and Cooperative Economic Development, which was established and mandated to understand conditions in the origin countries that result in undocumented migration and propose mitigations, recommended a host of economic development policies to reduce migration in the long term (USCSIMCED 1990). More recently, the US Citizenship Act of 2021, introduced in the House of Representatives, seeks to address the “root causes of migration”— such as institutional corruption, violence, and extreme poverty—in the origin countries, along with reforming the US immigration system to benefit all parties (Sánchez 2021). Likewise, the European Commission’s position on migration, drafted in the wake of the Syrian refugee crisis, identifies civil war, persecution, poverty, and climate change as root causes of migration (European Commission 2015). The European Union Emergency Trust Fund for Africa, established with a €5 billion endowment to address the root causes of undocumented migration and forced displacement in selected African countries, also emphasizes enhancing economic opportunities in origin countries as a key strategic objective.<sup>4</sup> But a closer look at the data suggests that the relationship between economic development and emigration is not straightforward. As Figure 1 shows, it is neither the highest-income nor the lowest-income countries that have the highest emigration rates. Low-income countries like Ethiopia, Madagascar, and Tanzania, as well as high-income countries like Japan, Qatar, and the United States, have fewer than 1 percent of their population as emigrants abroad. In contrast, emigration rates are highest for middle-income countries such as Albania, the Dominican Republic, and Lebanon.<sup>5</sup> This relationship—the inverted-U shape between income and migration where migration is highest at intermediate income levels—has been labeled the _mobility transition_ (Zelinsky 1971), the _migration hump_ (Martin and Taylor 1996), and the _emigration life cycle_ (Hatton and Williamson 1994).<sup>6</sup> In other words, the propensity to migrate may increase, not decrease, as countries develop.

> 1 The poverty rate is based on the rate of $1.90 per capita per day. Poverty calculations are based on data from the World Bank Poverty & Inequality Platform: <u>https://pip.worldbank.org/home.</u>

> 2 COVID-19 is expected have an adverse impact on poverty, pushing some 100 million people into poverty in 2020 alone (World Bank 2020). 3 Unless otherwise mentioned, this paper will measure incomes in terms of GDP per capita in constant 2017 US dollars in purchasing power parity terms (2017 PPP$) as established by the Penn World Tables (PWT) 10.0 release (Feenstra, Inklaar, and Timmer 2015).

> 4 <u>https://ec.europa.eu/trustfundforafrica/index_en</u>

> 5 Even after adjusting for the population of the countries, low-income countries have about the same migration rate as middle-income countries. 6 See, for instance, Clemens (2014); Dao et al. (2018); Djajić, Kirdar, and Vinogradova (2016) for studies on the cross-sectional relationship between migration and development.

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