April 3 (Bloomberg) -- Last week, the U.S. Senate began considering major reforms of immigration and border-security legislation, elevating a simmering issue into an explosive national debate. Of all the proposals out there, only one has its economics right.

Right now in the Senate, the two major plans being debated are from Majority Leader Bill Frist and Judiciary Committee Chairman Arlen Specter. Frist's bill focuses primarily on border protection, and has been characterized as an ``enforcement only'' proposal. Specter's proposal borrows from a bill that Senators John McCain and Ted Kennedy introduced last year. It includes provisions for temporary guest worker visas and for legalizing the status of currently undocumented individuals.

Both bills exist because lawmakers and citizens are worried about illegal immigration. The best estimates suggest about 12 million individuals reside in the U.S. illegally. Since essentially anyone born in the U.S. has a right to citizenship, many illegal immigrants have become parents of legal citizens, and productive members of their communities. Accordingly, despite the heat of the debate, any plan to round up existing illegals and send them home is politically dead on arrival.