This paper examines the causal effect of weather variations on agricultural productivity and international migration.
The authors employ a two-stage least square (2SLS) empirical approach, whereby they first regress climate variables on agricultural outcomes, and then regress the predicted agricultural outcomes on migration. The analysis is based on data on 108 poor and middle-income countries from 1960 to 2010 covering international migration, temperature and precipitation, agricultural output and agricultural productivity, proportion of land area that is irrigated, per capita income, conflict, quality of institutions, life expectancy at birth, export diversification, and diaspora networks in destination countries. The data indicates that:
- The average migration rate in the period considered (1960–2010) is 2.9 percent (2.4 percent for low-income countries and 3.5 percent for the middle-income countries).
- The agricultural share of GDP in low-income countries (31 percent) is more than twice that in middle-income countries (13 percent).
- The proportion of agricultural areas with irrigation (a measure of vulnerability to climate change), is 24 percent in middle-income countries but only 16 percent in low-income countries.
The authors demonstrate empirically that negative shocks to agricultural productivity caused by climate fluctuations significantly increase net migration outflows for developing countries overall, and for low-income countries. A climate-driven reduction in agricultural productivity of 1 percent below trend, over a 10-year period, induces an additional increase in the emigration rate from about 2.5 percent overall, to about 4.5 percent in poor countries. There is not a statistically significant effect in middle income countries.
The authors conclude that negative shocks to agricultural productivity caused by (long-run) weather variation positively affect net migration outflows. The climate-agricultural-migration nexus is particularly strong for poor and most vulnerable countries, where the agricultural sector represents the main income stream of the population, is more vulnerable to climate shocks, and where people are more likely to use migration as an adaptation response strategy.