(NAFTA), the free trade agreement between the U.S., Canada, and Mexico, was signed by President George H. W. Bush in December 1992, pending its ratification by the legislatures of the three countries. Clinton did not alter the original agreement, but complemented it with the North American Agreement on Environmental Cooperation and the North American Agreement on Labor Cooperation, making NAFTA the first "green" trade treaty and the first trade treaty concerned with each country's labor laws, albeit with very weak sanctions. NAFTA provided for gradually reduced tariffs and the creation of a free-trade bloc between the United States, Canada, and Mexico. Opponents of NAFTA, led by 1992 independent presidential candidate Ross Perot, claimed it would force American companies to move their workforces to Mexico, where they could produce goods with cheaper labor and ship them back to the United States at lower prices. Clinton, however, argued that NAFTA would increase U.S. exports and create new jobs. When he signed NAFTA, Clinton said: "NAFTA means jobs. American jobs, and good-paying American jobs. If I didn't believe that, I wouldn't support this agreement." He convinced many Democrats to join most Republicans in supporting trade agreement and in 1993 the Congress passed the treaty. While economists generally view free trade as an overall positive for the nation's involved, certain groups may be adversely affected, such as manufacturing workers. For example: In a 2012 survey of leading economists, 95% supported the notion that on average, U.S. citizens benefited on NAFTA. A 2001 Journal of Economic Perspectives review found that NAFTA was a net benefit to the United States. A 2015 study found that US welfare increased by 0.08% as a result of the NAFTA tariff reductions, and that US intra-bloc trade increased by 41%. In 2015, the Congressional Research Service concluded that the "net overall effect of NAFTA on the U.S. economy appears to have been relatively modest, primarily because trade with Canada and Mexico accounts for a small percentage of U.S. GDP. However, there were worker and firm adjustment costs as the three countries adjusted to more open trade and investment among their economies." CRS also pointed out that NAFTA to a great extent set rules for behavior already underway (e.g., U.S. manufacturing companies were already moving some jobs to Mexico, thus avoiding U.S. employment regulation and unions, in efforts to maximize profits.) The United States Chamber of Commerce credits NAFTA with increasing