A meta-analytic assessment of the effect of immigration on wages

In our increasingly interconnected and open world, international migration is becoming an important socioeconomic phenomenon for many countries. Since the early 1980s, many studies about the impact of immigration on host labour markets have been undertaken. Borjas (2003, The labor demand curve is downward sloping: reexamining the impact of immigration on the labor market. Quarterly Journal of Economics 118(4): 1335-1374) noted that the estimated effect of immigration on the wage of native workers varies widely from study to study and sometimes even within the same study. In addition, these effects cluster around zero. Such a small effect is a rather surprising outcome, given that in a closed competitive labour market an increase in labour supply may be expected to exert a downward pressure on wages. We revisit this issue by applying meta-analytic techniques to a set of 18 papers, which altogether generated 348 estimates of the percentage change in the wage of a native worker with respect to a 1 percentage point increase in the ratio of immigrants over native workers. While many studies in our database employ US data, estimates are also obtained from Germany, The Netherlands, France, Norway, Austria, Israel and Australia. Our analysis shows that results vary across countries and are inter alia related to the type of modelling approach. Technical issues such as publication bias and quality of the estimates are addressed as well.