This paper derives the conditions under which fitness-reducing alleles can survive in a long-run stationary equilibrium for a trading population, extending the results in Saint-Paul (2002) for arbitrary systems of sexual reproduction.

I show how the influences of unskilled immigration, differential fertility between immigrants and the local indigenous population, and incentives for investment in human capital combine to predict the decline of the West. In particular, indigenous low-skilled workers lose from unskilled...