ONE of the many oddities of migration policy is that immigrants coming in to work permanently are usually a minority of those who arrive legally. Most host countries admit migrants mainly on grounds that have nothing to do with work. They also admit two large groups on grounds that have nothing to do with their skills or education, even though these characteristics may determine how rapidly they integrate.

Almost everywhere, the biggest group consists of relatives of those who have already arrived. In the United States they account for three-quarters of all legal permanent migrants. America even gives a few visas to migrants' adult siblings. In parts of Europe, family reunification has become family formation, and sometimes delays integration: for instance, it allows third-generation Pakistanis to seek spouses from among their cousins back in rural Mirpur. The policy also reinforces the characteristics of earlier arrivals. Unskilled migrants are likely to have less educated relatives than are skilled migrants.

Panos

Where can we send them now?

In Europe, and especially northern Europe, the other main route of legal entry is to claim asylum. The number of claims has fallen by half since the early 1990s, partly because peace has returned to former Yugoslavia, and partly because of tougher rules, but still seems to be higher than in the United States. America cut the numbers sharply after the first attack on the World Trade Centre in 1993, mainly by refusing to allow asylum-seekers to work or draw any welfare benefits for the first six months of their stay, and by speeding the claims process. Many European countries are now moving that way.

Both marriage and asylum-seeking are clearly open to abuse by the desperate or the unscrupulous. Many asylum-seekers are fleeing poverty and disorder rather than persecution. It is usually impossible to establish whether or not they have really suffered the traumas they claim. Certainly there are some odd things going on. Near Calais, a large group of Iranians and Afghans have long been encamped, refusing to claim asylum until they have reached Britain.

When it comes to student visas, there are incentives to cheat not only for would-be immigrants but for educational institutions too. Harvard University's Mr Borjas explains in a recent article in the National Review that 13% of foreign students stay on legally, making a place at an American educational establishment a safer bet for an entry ticket than the 0.5% chance of winning the annual American visa lottery. The incentive for educational bodies of all sorts is that foreign students provide welcome tuition fees and, for universities, cut-price teaching help.

One reason why would-be immigrants choose these roundabout routes to the rich world is that there are few straightforward ones available. Migrating for a permanent job is difficult everywhere. Canada has a system, copied by Australia, for admitting a few thousand would-be immigrants each year on the basis of points awarded for a variety of characteristics. Increasingly, says Meyer Burstein, a Canadian expert, these reward skills, education, language and youth. Germany and Britain both want to copy Canada's system, whereas Americans think that the job market is the best judge of what is needed. But even in America, says John Salt of University College London, a top expert on migration, “Highly skilled permanent employment-based immigrants account for about 3% of the total number of immigrants.”

Temporary work permits, which several countries increasingly issue, help a bit to fill the gap, but most involve a process of labyrinthine complexity. Often there is a test of some sort to ensure that the worker is not taking a job that a native might fill—usually a meaningless formality, but one of several that allow endless opportunities for bureaucratic delay. That seems even more true for the United States than for Europe. Leon Wildes, the New York immigration lawyer who got John Lennon a work permit in the heyday of the Beatles, taps a vast blue file on his desk. “This is one of my most well-heeled clients. He wants to bring in his household cook. It's taken us four-and-a-half years to get to this point.”

Because work permits are rarely issued to the unskilled, such people generally have no legal way of migrating to find work. So they come illegally. Immigration controls keep many people out, but not everyone. Vast numbers of travellers enter and leave most countries each year. For instance, although 20m foreigners arrive in Britain each year, Professor Salt's best guess is that Britain's foreign population rose by a mere 134,000 between 1999 and 2000. But even islands will never catch all those with no right to be there: most illegals are visitors who overstay their tourist or student visas.

If a country has a long land border, like the United States, or coasts temptingly near poorer countries, like Italy, its best hope is internal enforcement. That is easier in countries such as Germany, where people have to carry identification and register with the local authorities when they move. But even Germany has asylum-seekers who vanish when their claim is turned down: “We call them U-boats,” says Rainer Münz, a demographer at Berlin's Humboldt University.

Either way, the illegals keep on coming. More than a quarter of America's immigrants, or about 9m people, are probably undocumented: about 60% of them entered illegally and 40% overstayed their visas. Their number grows by at least 500,000 a year, reckons Jeffrey Passel of the Urban Institute. Mexicans are more likely to be undocumented than any other group: the Immigration and Naturalisation Department thinks that 88% of male Mexicans and 73% of female ones entering America have no papers. That compares with 53% of men and 34% of women from the rest of the western hemisphere.

Numbers for Europe are vaguer. Jean-Claude Chenais, a leading French demographer, guesses that Germany has 1m and France up to 500,000 illegals. Jonas Widgren, head of the International Centre for Migration Policy Development in Vienna, thinks that 500,000 illegal migrants enter the EU each year. Most cross land or sea borders illegally, he says, but 150,000 overstay their visas. That implies that the inflow into Europe and the United States is much the same, relative to population: about 0.15% of population a year.

Visit the American-Mexican border patrol at El Paso, and the problem is plain. No border crossing in the world has more sophisticated detection equipment. Cameras monitor remote stretches; a chain-link fence spans miles of scrubland; sensors buried in roads draw attention to suspicious traffic; patrols on horseback and quad bikes sweep the desert, dragging car tyres to smooth the sand and make it easier to spot fresh footprints. For all this expense and the consequent human misery, the patrol reckons it catches six or seven of every ten illegal entrants. A large proportion of the 400 people apprehended each day—and usually released—have crossed, or tried to cross, before.

Thousands continue to climb into the backs of the trucks that carry the world's trade across borders, to the fury of the International Road Transport Union, whose members pay fines or even go to jail when their unwanted cargo is discovered. Many would-be immigrants use the services of a professional smuggler. The rich world's politicians tend to talk of migrants being “exploited” or “victimised” by smugglers, wilfully confusing them with the traffickers who buy and sell women and children in the sex trade. Some smugglers are undoubtedly ruthless, and becoming more so as smuggling fees rise. But many would-be migrants, having decided to go, seek out the services of a smuggler on a friend's recommendation, rather as holidaymakers turn to a travel agent.

After border checks, the only backstop is internal enforcement. Illegals thrive on vigorous, open labour markets in societies with few internal checks. In a remarkable study of undocumented immigrant workers in London for a conference run by the Institute of Public Policy Research in March, Bill Jordan and Frank Düvell reported an interview with a Pole who had been in London for seven years, during which time he worked (illegally) continuously and trebled his hourly earnings:

I have been to Germany three or four times ...You earn better money there but there is no freedom: you have to be able to produce your documents at any time, whereas here ...nobody ever asked to see my passport. I would never have been able to live illegally in Germany for so many years.

Internal enforcement inevitably means making employers responsible for ensuring that their staff have a legal right to work. That is possible in Germany, where employers are used to bureaucratic demands. In the United States, Doris Meissner, formerly head of the Immigration and Naturalisation Service, recalls with frustration the impossibility of enforcing effective controls on employers. When the INS inspectors harried them, bosses simply told politicians that without illegals the harvest would rot in the fields. Stephen Castles, director of the Refugee Studies Centre at Oxford University, puts his finger on the problem: “You'd actually have to imprison employers. Would the courts do it?” At present, even fines are rare.

Even if employers could be disciplined, countries would then need to be able to remove those who arrive illegally. This is difficult everywhere. In the spick-and-span El Paso detention centre, America's largest, officials sigh if the courts hand down a deportation order for illegals from Cuba, Iran or Iraq. Releasing the immigrant is far simpler than trying to send him home.

Even if countries could be cajoled or bullied into taking back their strays, no imaginable repatriation policy is likely to evict all illegals, so their reluctant hosts need to find ways to deal with them. The alternative is to put up with an underworld population of non-persons, who may be unable to get car insurance or health care and who may pay no income tax or social-security contributions.

Having become increasingly wary about links between immigration and security, countries understandably feel uncomfortable about the presence of millions of undocumented foreigners. But offer them an amnesty, as America, in effect, did to 3m people in 1986 and Malaysia did in May this year, and you give others an incentive to try their luck. The wiser compromise is to allow those who have found work, paid taxes and avoided trouble to earn the right to stay, rather than force them home to change their status. In general, the benefits of being able to regulate those who have become legal will outweigh the costs of appearing to cave in. “The attitude of the public will depend on how you package it,” says Esther Olavarria, counsel to Senator Edward Kennedy, who is keen to help the undocumented. “If you say it's an amnesty, they'll say no. But if you say, these are hard-working individuals whose position needs to be regularised, they'll support it.”

And rightly. Illegal migrants are the most employment-hungry, market-sensitive arrivals of all. In the United States, points out Roberto Suro, director of the Pew Hispanic Centre, they provide just-in-time labour: “A meat-packing plant in Iowa can say to the foreman, next month we need 5% more workers for three months. On the day they are needed, they'll be there. It's extremely efficient.”

To convince their voters that migration is under control, governments have to curb the illegal sort. But they would be foolish, in doing so, to lose the flexibility and employability that illegals contribute. Better to find ways to allow more to come legally—but not necessarily to stay.

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