'With two friends I started a journey to Greece, the most horrendous of all journeys. It had all the details of a nightmare: barefoot walking in rough roads, risking death in the dark, police dogs hunting us, drinking water from the rain pools in the road and a rude awakening at gunpoint from the police under a bridge. My parents were terrified and decided that it would be better to pay someone to hide me in the back of a car.' This 16-year-old Albanian high-school drop-out, desperate to leave his impoverished country for the nirvana of clearing tables in an Athens restaurant, might equally well have been a Mexican heading for Texas or an Algerian youngster sneaking into France. He had the misfortune to be born on the wrong side of a line that now divides the world: the line between those whose passports allow them to move and settle reasonably freely across the richer world's borders, and those who can do so only hidden in the back of a truck, and with forged papers. Tearing down that divide would be one of the fastest ways to boost global economic growth. The gap between labour's rewards in the poor world and the rich, even for something as menial as clearing tables, dwarfs the gap between the prices of traded goods from different parts of the world．The potential gains from liberalizing migration therefore dwarf those from removing barriers to world trade. But those gains can be made only at great political cost. Countries rarely welcome strangers into their midst. Everywhere, international migration has shot up the list of political concerns. The horror of September 11thhas toughened America's approach to immigrants, especially students from Muslim countries, and blocked the agreement being negotiated with Mexico. In Europe, the far right has flourished in elections in Austria, Denmark and the Netherlands. Although many more immigrants arrive legally than hidden in trucks or boats, voters fret that governments have lost control of who enters their country. The result has been a string of measures to try to tighten and enforce immigration rules. But however much governments clamp down, both immigration and immigrants are here to stay. Powerful economic forces are at work. It is impossible to separate the globalisation of trade and capital from the global movement of people. Borders will leak; companies will want to be able to move staff; and liberal democracies will balk at introducing the draconian measures required to make controls truly watertight. If the European Union admits ten new members, it will eventually need to accept not just their goods but their workers too. Technology also aids migration. The fall in transport costs has made it cheaper to risk a trip, and cheap international telephone calls allow Bulgarians in Spain to tip off their cousins back home that there are fruit-picking jobs available. The United States shares a long border with a developing country; Europe is a bus ride from the former Soviet block and a boat-ride across the Mediterranean from the world's poorest continent. The rich economies create millions of jobs that the underemployed young in the poor world willingly fill. So demand and supply will constantly conspire to undermine even the most determined restrictions on immigration. The author cites the example of the 16-year-old Albanian high-school drop-out to show