He cites this example from the tomato growing industry:
Economist Philip Martin of the University of California likes to tell a story about the state's tomato industry. In the early 1960s, growers relied on seasonal Mexican laborers, brought in under the government's ``bracero'' program. The Mexicans picked the tomatoes that were then processed into ketchup and other products. In 1964, Congress killed the program despite growers' warnings that its abolition would doom their industry. What happened? Well, plant scientists developed oblong tomatoes that could be harvested by machine. Since then, California's tomato output has risen five times.
And he finds no benefit from importing poverty.
What we have now -- and would with guest workers -- is a conscious policy of creating poverty in the United States while relieving it in Mexico. By and large, this is a bad bargain for the United States. It puts stresses on local schools, hospitals and housing; it feeds social tensions (witness the Minutemen).
It's a good read for anyone confused by the arguments that our economy is dependent on illegals. Read it here.