Lou Dobbs, take note: immigrants are good for our economy. The most skilled create jobs in technology and engineering, says Duke professor Vivek Wadhwa, who estimates that in 2005 immigrant-founded engineering and tech companies employed 450,000 people and generated $52 billion in sales. But even the least skilled more than repay their costs in schools and health care. Two highly respected Australian economists, Maureen Rimmer and Peter Dixon, studied the issue for the libertarian Cato Institute. "The net impact on U.S. households from tighter border enforcement is unambiguously negative," they found, because even low-skilled immigrants expand the economic pie and create jobs farther up the ladder. Cato's Dan Griswold says the study shows a $250 billion difference between the most and least restrictive immigration policies.