Much of the NAFTA debate in the U.S. in the 1990's revolved around the concern among U.S. labor unions and others that low- and semi-skilled U.S. jobs would be lost to Mexico since those jobs were concentrated in the production of goods that could be imported rather than produced domestically. This concern reflects what basic result from international trade? Group of answer choices The Rybczinski Theorem The Smith-Ricardo Proposition The Stolper-Samuelson Theorem The Leontief Paradox None of the listed answers