In most OECD-countries, immigrants have lower employment and higher unemployment than natives. This paper compares nine potential explanations of these gaps. Results are obtained for 21-28 countries using bivariate correlations, OLS-regressions and Bayesian model averaging over all 512 theoretically possible model specifications. Two robust patterns are found. The unemployment gap is bigger in countries where collective bargaining agreements cover a larger share of the labor market. The employment gap is bigger in countries with more generous social safety nets. Five variables have explanatory value in some specifications: Xenophobia, employment protection laws, social expenditure, asylum applications, and the share of immigrants in the population. The education of immigrants and migrant integration policies have no explanatory value. A trade-off seems to exist such that countries with smaller labor market gaps have higher income inequality.