SAN FRANCISCO (By Dean E. Murphy, NYTimes) January 11, 2004 — Imagine America without undocumented immigrants, the people who flip the burgers, clean the toilets, watch the kids and send their children to public schools.

Would the grass be greener?

The question got an answer of sorts last month in California, where about a third of the country's estimated 8 million to 10 million undocumented immigrants live. Thousands of Hispanics stayed home from school and work one Friday, protesting the repeal of a contentious new law that would have allowed undocumented immigrants to obtain driver's licenses.

The boycott was not nearly the success its organizers had hoped for. Nonetheless, there were reports of fast-food counters closing and lawns going uncut. A few shops in cities with big immigrant populations, like Fresno, did not bother opening, and in Los Angeles, the second-largest school district in the country, the absentee rate nearly tripled from the Friday before.

President Bush reopened the national debate about immigration last week with his proposal to grant temporary visas to undocumented workers. As with those who supported the repeal of the driver's license law in California, the Bush initiative left many Americans wondering why elected officials would change the rules for people who live in this country only by breaking them.

"I think it is hard to imagine a worse immigration reform proposal right now," said George J. Borjas, a professor of economics and social policy at Harvard who has written extensively about the drawbacks of undocumented immigration. "The one good thing you could say about it is, it takes seriously the fact that the United States is not going to deport 10 million people. We have to do something about these people."

Most everyone would agree that mass deportation is unlikely. But imagining such a chain of events is one way of understanding the economic backdrop to Mr. Bush's initiative.

The Pew Hispanic Center estimated in 2001 that the unauthorized labor force in the United States totaled 5.3 million workers, including 700,000 restaurant workers, 250,000 household employees and 620,000 construction workers. In addition, about 1.2 million of the 2.5 million wage-earning farm workers live here undocumentedly, according to a study by Philip L. Martin, a professor at the University of California at Davis who studies immigration and farm labor.

That is a whole lot of cheap labor.

Without it, fruit and vegetables would rot in fields. Toddlers in Manhattan would be without nannies. Towels at hotels in states like Florida, Texas and California would go unlaundered. Commuters at airports from Miami to Newark would be stranded as taxi cabs sat driverless. Home improvement projects across the Sun Belt would grind to a halt. And bedpans and lunch trays at nursing homes in Chicago, New York, Houston and Los Angeles would go uncollected.

"There would be a ripple effect across the economy," said Harry P. Pachon, president of the Tomás Rivera Policy Institute at the University of Southern California, a Hispanic research group.

Estimates by the Immigration and Naturalization Service based on the 2000 census show that 15 states accounted for all but 13 percent of undocumented immigrants.

Laura Hill, a research fellow at the nonpartisan Public Policy Institute of California, said there would be a spike in prices for lettuce, spinach and strawberries, which are typically picked by undocumented workers. But farmers and agricultural companies would eventually find cheaper ways to harvest the crops. "Who knows, but maybe it would turn into new technology being developed," Ms. Hill said.

If not, Americans would look elsewhere, including other countries, for cheaper substitutes.

But immigrant advocacy groups dispute the notion that undocumented immigration is a drag on America. Raul Yzaguirre, president of the National Council of La Raza, a Hispanic civil rights organization, said the economic impact of immigration plays out differently at the local and national levels.

While hospitals and clinics in Los Angeles County, for example, bear huge health care costs associated with uninsured undocumented immigrants - one study put the total at $340 million in 2002 - the federal government enjoys a "bonanza" from many of the same immigrants who pay federal taxes but receive no benefits in return, Mr. Yzaguirre said.

Mr. Yzaguirre suggested that Social Security would go broke without the payments of undocumented workers, many of whom, contrary to popular perception, do have regular payroll taxes deducted from their paychecks by employers. (In some instances, undocumented workers use false Social Security numbers, while others have valid numbers from when they had worked legally.)

Mr. Yzaguirre also rejected suggestions that Americans would maintain their standard of living without the low-wage contributions of those workers. He agreed with Professor Borjas that some Americans would enjoy fatter paychecks, but he said all Americans would be punished by having to pay more for everything from a McDonald's hamburger to a new house.

In a 2002 study conducted with the cooperation of immigrant rights organizations, researchers at the Center for Urban Economic Development at the University of Illinois at Chicago concluded that the 300,000 or so undocumented immigrants in Chicago did not use government benefits at a substantial rate. The study also estimated that 70 percent of the undocumented workers paid payroll taxes, like Social Security and unemployment insurance. The researchers calculated other economic benefits, finding that consumer spending by undocumented migrants generated more than 31,000 jobs and contributed $5.34 billion annually to the gross regional product in Chicago.

Which side to believe? The problem with gathering data about undocumented immigrants, and the idea of an America without them, is that they tend to blend into the vast tapestry of legal immigrants.

Someone living and working in the United States with a valid visa one year can become undocumented the next by overstaying the visa. A single household can have legal and undocumented residents, sometimes brothers and sisters. In that sense, the Bush proposal to blur the distinction further between undocumented and legal workers includes "some degree of honesty," said Patricia Nelson Limerick, chairwoman of the Center of the American West at the University of Colorado.

"The hope is that it would lead to some recognition that you don't solve problems of undocumented immigration by shutting down the border," she said, "but reckoning with the problems in the home country."