Migrations may be region-specific or they may be transcontinental or transoceanic. In the so-called Age of Revolution in the Atlantic World, British and continental European anti-revolutionary warfare made migration perilous. The hemisphere-wide migrations systems are emerged of men and women moving independently, in family units, or sequentially as families or siblings. Discrimination against resident minorities and to enforce assimilation male state bureaucracies added a new type of forced migration motivated by nationalism. In the 1960s, decolonization, new markets, intensifying economic relations, and new alignments led to major revisions of immigration policies. 'Global apartheid', dividing South and North, extreme exploitation of many migrant workers, displacement by environmental deterioration and developmental projects, an assumed 'feminization' and globalization of migration all characterize migration in the early twenty-first century, and form the major themes of research. Migrants, who carefully assess costs and rewards of their moves, are entrepreneurs in their own lives, trying to make the most of their human capital.