This document summarizes research on global migration patterns from 1950-2000. It finds that the stock of migrants as a percentage of populations has increased in North America, Oceania, and Europe, but declined elsewhere. Major migration flows proceed from less developed to more developed countries. While migration rates have increased in recent decades, they remain lower than during previous periods of mass migration. Theories discussed to explain migration trends include neoclassical economics, segmented labor market theory, and cumulative causation theory. Consequences on sending countries include loss of skilled labor but economic gains from remittances. Impacts on receiving countries are small and include changes to labor force composition rather than unemployment or wage impacts.