How would closing the border with Mexico affect the U.S. economy?

I've heard it said that without illegal aliens to do our drudge work, we'd have to pay legal citizens a lot more money to do the same work, we'd have to give them health insurance and dental and medical and our economy would sour without illegal aliens. Remember it's not the illegal aliens that are the problem, it's the Americans who are using their cheap services that are the problems here.
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It will reduce the effects of trade creation under NAFTA, and might increase the trade diversion that is harmful to the US economy. Hugh government budget is required to enforce the law. The US would have lost the oppotunity to employ cheap labors, and in some cases creativity.
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