WASHINGTON (By Nina Bernstein, NYTimes) December 7, 2005 — A report about the work lives of recent Mexican immigrants in seven cities across the United States suggests that they typically traded jobs in Mexico for the prospect of work here, despite serious bouts of unemployment, job instability and poor wages.

The report, released Tuesday by the Pew Hispanic Center, was based on surveys of nearly 5,000 Mexicans, most of them here illegally.

Those surveyed were seeking identity documents at Mexican consulates in New York, Atlanta and Raleigh, N.C., where recent arrivals have gravitated toward construction, hotel and restaurant jobs, and in Dallas, Chicago, Los Angeles, and Fresno, Calif., where they have been more likely to work in agriculture and manufacturing.

Unlike the stereotype of jobless Mexicans heading north, most of the immigrants had been employed in Mexico, the report found.

Once in the United States, they soon found that their illegal status was no barrier to being hired here. And though the jobs they landed, typically with help from relatives, were often unstable and their median earnings only $300 a week, that was enough to keep drawing newcomers because wages here far exceeded those in Mexico.

"We're getting a peek at a segment of the U.S. labor force that is large, that is growing by illegal migration, and that is bringing an entirely new set of issues into the U.S. labor market," said Rakesh Kochhar, associate director for research at the Pew Hispanic Center and author of the study.

The report suggested that policies intended to reduce migration pressures by improving the Mexican economy would have to look beyond employment to wages and perceptions of opportunity.

The survey found that the most recent to arrive were more likely to have worked in construction or commerce, rather than agriculture, in Mexico. Only 5 percent had been unemployed there; they were "drawn not from the fringes, but from the heart of Mexico's labor force," the report said.

After a difficult transition in their first six months in the United States - about 15 percent of the respondents said they did not work during that time - the rate of unemployment plummeted, to an average of 5 percent.

But in one of the most striking findings, 38 percent reported an unemployment spell lasting a month or more in the previous year, regardless of their location, legal status or length of time in the United States.

"These are workers with no safety net," Mr. Kochhar said. "The long-run implication is a generation of workers without health or pension benefits, without any meaningful asset accumulation."

On the other hand, Mr. Kochhar and Roberto Suro, director of the Pew Hispanic Center, said the flexibility of this work force was a boon to certain industries like home construction, an important part of the nation's economic growth since the last recession.

Among respondents to the survey, those who settled in Atlanta and Dallas were the best off, with 56 percent in each city receiving a weekly wage higher than the $300-a-week median. The worst off were in Fresno, where more than half of the survey respondents worked in agriculture and 60 percent reported earning less than $300 a week. The lowest wages were reported by women, people who spoke little or no English, and those without identification.

To some scholars of immigration, the report underlines the lack of incentives for employers to turn to a guest worker program like the one proposed by President Bush because their needs are met cheaply by illegal workers - and all without paperwork or long-term commitment.

Guest workers might instead appeal to corporations like Wal-Mart, the scholars said, where service jobs are now the target of union organizing drives.

"You can't plausibly argue that immigrant-dominated sectors have a labor shortage," said Robert Courtney Smith, a sociologist and author of "Mexican New York: Transnational Lives of New Immigrants." Instead, he said, the report and evidence of falling wages among Mexican immigrants over time point to an oversupply of vulnerable workers competing with each other.

But Brendan Flanagan, a spokesman for the National Restaurant Association, which supports a guest worker program, disagreed. "In many places it is difficult to fill jobs with domestic workers," Mr. Flanagan said. "We've seen a simple lack of applicants, regardless of what wage is offered."

Although the survey, conducted from July 2004 to January 2005, was not random or weighted to represent all Mexican immigrants, it offers a close look at a usually elusive population.

Those surveyed were not questioned directly about their immigration status, but they were asked whether they had any photo identification issued by a government agency in the United States. Slightly more than half over all, and 75 percent in New York, said they did not.

The migration is part of a historic restructuring of the Mexican economy comparable to America's industrial revolution, said Kathleen Newland, director of the Migration Policy Institute, a research organization based in Washington.

The institute released its own report on Tuesday, arguing that border enforcement efforts have failed. Workplace enforcement, which has been neglected, would be a crucial part of making a guest worker program successful.

For now, Mexicans keep arriving illegally.

"It doesn't matter if it's winter," said Ricardo Cortes, 23, a construction worker waiting for a friend outside the Mexican consulate in New York on Tuesday. "People are still coming because there's no money over there."