Now that the Senate has slowed down the “amnesty” process a bit (phew!), perhaps they will be able to thoughtfully examine the economic impact of allowing massive numbers of low-skilled immigrant workers into this country (whether they’re here illegally or not). This isn’t to say that we shouldn’t allow such workers in, only that we shouldn’t allow so many–and we certainly shouldn’t do so by enabling illegal entry by “looking the other way.”
It is often argued that the American economy relies on low-skill immigrants–illegal or not–who can be paid a low wage to perform the “jobs Americans won’t do.” What is left unsaid is that these workers effectively hold down the wages of American citizens, as this study {PDF} shows.

• By increasing the supply of labor between 1980 and 2000, immigration reduced the average annual earnings of native-born men by an estimated $1,700 or roughly 4 percent.
• Among natives without a high school education, who roughly correspond to the poorest tenth of the workforce, the estimated impact was even larger, reducing their wages by 7.4 percent.
• The 10 million native-born workers without a high school degree face the most competition from immigrants, as do the eight million younger natives with only a high school education and 12 million younger college graduates.
• The negative effect on native-born black and Hispanic workers is significantly larger than on whites because a much larger share of minorities are in direct competition with immigrants.
• The reduction in earnings occurs regardless of whether the immigrants are legal or illegal, permanent or temporary. It is the presence of additional workers that reduces wages, not their legal status.

Further, this study examines the specific impact that that low-skilled, non-native laborers have on African-American workers. Another argument is that we need these low-wage, low-skill (illegal) immigrant workers in our fields so that we Americans can pay low prices for such things as apples and lettuce. I’ve gotta admit that this one always made sense to me. But I may be wrong.

One of the most frequently asked questions is what would happen to US food prices if legal and unauthorized farm workers were not readily available. It is important to emphasize that most of the flexibility in the farm labor market is on the demand, not the supply side. For example, when wages increased in the past, farmers responded by producing food with fewer workers, not by inducing more Americans to do farm work. Generally, substituting capital (machines) for workers reduced food prices.
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In order to determine how much raising farm worker wages would affect food prices, we have to know: (1) the farmer’s share of retail food prices, as well as; (2) what share farm worker wages and benefits are of farmer revenue or costs. For most fruits and vegetables, wages and benefits paid to farm workers are about one-third of a farmer’s costs. Thus, farmers who get about $0.16 for a $1 pound of apples, and $0.19 for a $1 head of lettuce, have farm-worker costs of 5-6 cents on a typical $1 retail item of produce.
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If a 40 percent farm-worker wage increase were fully passed on to consumers, and if there were no farm productivity improvements in response to higher farm wages, the 5-6 cent farm labor cost of a pound of apples or a head of lettuce would rise to 7-8 cents, and the retail price would rise from $1 to $1.02-$1.03.
A large increase in farm wages translates into a small retail cost increase because: (1) farm labor is a third of farmers’ costs; and (2) farmers receive only a fraction of the retail price of food. For a typical 2.5-person consumer unit, a 40 percent increase in farm worker wages that led to a three percent increase in retail fresh fruit and vegetable costs would increase the spending of a typical consumer unit by $9 a year, raising expenditures from $301 to $310.
For more information: (www.ers.usda.gov/publications/agoutlook/)

Finally, this study explains the cost-benefit of having a low-skilled, non-native work force:

In FY 2004, low-skill immigrant households received $30,160 per household in immediate benefits and services (direct benefits, means-tested benefits, education, and population-based services). In general, low-skill immigrant households received about $10,000 more in government benefits than did the average U.S. household, largely because of the higher level of means-tested welfare benefits received by low-skill immigrant households.
In contrast, low-skill immigrant households pay less in taxes than do other households. On average, low-skill immigrant households paid only $10,573 in taxes in FY 2004. Thus, low-skill immigrant households received nearly three dollars in immediate benefits and services for each dollar in taxes paid.
A household’s net fiscal deficit equals the cost of benefits and services received minus taxes paid. When the costs of direct and means-tested benefits, education, and population-based services are counted, the average low-skill household had a fiscal deficit of $19,588 (expenditures of $30,160 minus $10,573 in taxes).
At $19,588, the average annual fiscal deficit for low-skill immigrant households was nearly twice the amount of taxes paid. In order for the average low-skill household to be fiscally solvent (taxes paid equaling immediate benefits received), it would be necessary to eliminate Social Security and Medicare, all means-tested welfare, and to cut expenditures on public education roughly in half.
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Understanding of the fiscal consequences of low-skill immigration is impeded by a lack of understanding of the scope of government financial redistribution within U.S. society. It is a common misperception that the only indi­viduals who are fiscally dependent (receiving more in benefits than they pay in taxes) are welfare recipients who per­form little or no work, and that as long as an individual works regularly he must be a net tax producer (paying more in taxes than his family receives in benefits).
In reality, the present welfare system is designed primarily to provide financial support to low-income working families. Moreover, welfare is only a modest part of the overall system of financial redistribution operated by the gov­ernment. Current government policies provide extensive free or heavily subsidized aid to low-skill families (both immigrant and non-immigrant) through welfare, Social Security, Medicare, public education, and many other ser­vices. At the same time, government requires these families to pay little in taxes. This very expensive assistance to the least advantaged American families has become accepted as our mutual responsibility for one another, but it is fis­cally unsustainable to apply this system of lavish income redistribution to an inflow of millions of poorly educated immigrants.