Geographical human migration, including international, interregional, and interstate moves, is a very important form of human capital investment, and it has been receiving major popular and professional attention. We observe relatively high geographical migration rates near the time individuals complete their,formal schooling. Also, significant migration follows episodes of unemployment and plans to retire from the workforce. Frequently individuals return to the area where they were born, especially in retirement. The United Nations(1989, p.61) estimated that there are approximate 60 million people, or 1.2 percent of the world's population, now living in a country other than where they were born or in host (or foreign) countries. Over half of all immigrants go to the United States, Canada, or Australia. The U.S. has experienced a rapid increase in the size of immigrant flows and major changes in the national-origin composition of the immigrant population overtime. These changes are partly due to changes in the U.S. immigration policy. ^
Li, Yang and Huffman, Wallace E., "International Re-Migration Analysis: Evidence from Puerto Ricans" (1999). Economic Staff Paper Series. 313.