The world economy is becoming ever more integrated. Goods, capital, finance, technology and information flow across borders with increasing ease. Yet most people today remain firmly fixed in particular countries. The passport is now the universal symbol mof a world in which, like the serfs of the Middle Ages, we are all tied to a single piece of soil. This book examines migration as a response to changes in the world economy. He shows that despite tighter controls, increasing numbers of workers are moving, whether legally or nor, between countries. Unskilled immigrant workers play a vital role in improving standards of living in the developed world. In turn, the countries from which they have come benefit in a major way from the earnings sent back home. Arguing that few of the fears about immigration are justified, and that increased imigration tends to mean that jobs and incomes expand, this work shows why governments will have to ensure the freedom of people to come and go as they choose.