Today an estimated eight million or more people live in the United States without legal documents, and each year the number grows by an estimated 250,000 as more immigrants enter illegally or overstay their visas. More than half of those entering and already here come from Mexico.

Although the U.S. government has encouraged closer trade, investment, and political ties with Mexico, it has labored in vain to keep a lid on the flow of labor across the border. Since 1986, the numbers of tax dollars appropriated and agents assigned for border control have risen dramatically, yet by any real measure of results, the effort to constrict illegal immigration has failed.

Demand for low-skilled labor continues to grow in the United States while the domestic supply of suitable workers inexorably declines - yet U.S. immigration law contains virtually no legal channel through which low-skilled immigrant workers can enter the country to fill that gap. The result is an illegal flow of workers characterized by more permanent and less circular migration, smuggling, document fraud, deaths at the border, artificially depressed wages, and threats to civil liberties.

Legalizing Mexican migration would, in one stroke, bring a huge underground market into the open. It would allow American producers in important sectors of our economy to hire the workers they need to grow. It would raise wages and working conditions for millions of low-skilled workers and spur investment in human capital. It would free resources and personnel for the war on terrorism.

Contrary to common objections, evidence does not suggest that a properly designed system of legal Mexican migration will unleash a flood of new immigrants to the United States, hurt low-skilled Americans, burden taxpayers, create an unassimilated underclass, encourage lawbreaking, or compromise border security.

President Bush and leaders of both parties in Congress should return to the task of turning America's dysfunctional immigration system into one that is economically rational, humane, and compatible with how Americans actually arrange their lives.