Many proposals for a large US guest worker programme have been made during the past few years. George W. Bush,the president, suggests linking willing foreign workers with willing American employers. The argument is that foreign workers are needed to fill jobs that US nationals will not take, and legal admission is preferable to the massive clandestine entry that now takes place. Further, if undocumented entrants can come legally for temporary work, much of the elaborate mechanism in place to prevent surreptitious entry could be discarded.

Some data are needed to put such proposals in perspective. There are now about 11m undocumented immigrants in the US, including more than 6m Mexicans; and the annual inflow of undocumented Mexican immigrants is about 500,000. If a programme covering 500,000 legal temporary workers came into effect at, say, the start of 2006, this theoretically could eliminate almost all illegal entrants from Mexico for that year. The following year another 500,000 would be accepted, in 2008 the same and again indefinitely after that - at least until the domestic economic situation improved sufficiently for Mexicans to stop wanting to emigrate.