International migration, the movement of people across international boundaries to improve economic opportunity, has enormous implications for growth and welfare in both origin and destination countries. An important benefit to developing countries is the receipt of remittances or transfers from income earned by overseas emigrants. Official data show that development countries' remittance receipts totaled $160 billion in 2004, more than twice the size of official aid. This year's edition of Global Economic Prospects focuses on remittances and migration. The bulk of the book covers remittances, including their size, determinants, development impact, and steps to strengthen financial infrastructure and reduce transaction costs. It also presents available data on migration flows and examines current thinking on issues pertaining to migration and its development impact.