"People who hire illegal immigrants' bids come in so low we can't match that," he said. "We can't pay a decent wage, or a liveable wage. . . . We can't afford full benefits."

Wood says he pays $12 to $18 an hour. That can drop to as low as $3 to $4 an hour for those who hire illegals, he says.

While he tries to pay a "good top wage," Wood says over the past few years, his bids have declined. "Everybody is paying these guys under the table."

Wood says he requires all employees to present identification and fill out an I-9 form. When asked if he verified the information, he said he was unaware of any way to do so.

"Skin color, I don't care," he said. "Everybody should be paid a good wage . . . It's not a race matter, it's a matter of being fair."

William Hayden, business manager for Painters and Allied Trades Local 77, sees illegal immigration as a key reason for wages that have remained stagnant since the early 1990s, when Utah started to see an influx of Hispanic immigrants. Hayden says many of those workers are undocumented, and are often paid under the table by non-union employers, who avoid expenses such as state taxes and workman's compensation.

"The problem is, in residential (construction), undocumented workers are doing the majority of the work, and that's what basically sets the tone for wages," he said. "Employers get away with murder."

Hayden says his union, which represents about 160 people, tries to educate undocumented workers on what their wages should be.

His approach: "Trying to bring them up to our level rather than trying to keep them out."

Perlich says there are also important social justice issues often overlooked in this discussion.

In many cases, male workers come from Mexico to work and leave families behind. They send a big chunk of their income home. By some estimates, as many as one-third of workers in rural Mexico are in the United States working and sending money back to Mexico.

These circumstances give many employers license to behave cruelly and unethically to workers, Perlich said. "And what's their recourse?" she asked.

"If your status in this country depends on me and your paycheck depends on me," she said, "that's a lot of power I have over you."

Green lawns

Harvard professor of economics and social policy George J. Borjas is a national authority on the impact of illegal work on labor markets.

Without undocumented workers, industries would not collapse, but costs for services would go up, Borjas wrote in an excerpt from article in the National Review, "Making it Worse," February 2004.

For example, most gardeners in Southern California are Mexican immigrants, and many of them are illegal aliens.