NAFTA was supplemented by two other regulations: the North American Environmental Cooperation Agreement (NAAEC) and the North American Agreement on Labour Cooperation (NAALC). These tangential agreements should prevent companies from moving to other countries in order to use lower wages, more moderate health and safety rules and more flexible environmental rules. In 2015, the Congressional Research Service concluded that “NAFTA`s overall net impact on the U.S. economy appears to be relatively small, not least because trade with Canada and Mexico accounts for a small percentage of U.S. GDP. However, there have been adjustment costs for workers and businesses as the three countries have prepared for more open trade and investment between their economies. The report also estimated that nafta has added $80 billion to the U.S. economy since its inception, a 0.5% increase in U.S. GDP.  Under NAFTA, the three signatories agreed to remove barriers to trade between them. By removing tariffs, NAFTA has increased investment opportunities.
According to Chad P. Bown (Senior Fellow at the Peterson Institute for International Economics), it is unlikely that a renegotiated NAFTA, which would restore barriers to trade, will help workers who have lost their jobs, regardless of their cause, to use new employment opportunities.”  In June 1990, Mexican President Carlos Salinas de Gortari called for a free trade agreement with the United States. In September 1990, Reagan`s successor, President George H.W. Bush, began negotiations with President Salinas for a liberalized trade agreement between Mexico, Canada and the United States. In 2008, Republican candidate Ron Paul said he would abolish the trade agreement. He said he would create a “superautobahn” and compare it to the European Union, although NAFTA does not impose a single currency among its signatories. Economists generally agreed that the entire U.S. economy benefited from NAFTA by increasing trade.   In a 2012 survey by the Global Markets Initiative`s panel of economic experts, 95% of participants said that U.S. citizens benefited on average from NAFTA, while no one said that NAFTA was detrimental to U.S. citizens on average.
 A review of the 2001 Journal of Economic Perspectives showed that NAFTA was a net benefit to the United States.  A 2015 study showed that welfare in the United States increased by 0.08% and intra-block trade in the United States by 41% due to NAFTA tariff reductions.  According to a study in the Journal of International Economics, NAFTA has reduced pollution in U.S. manufacturing: “On average, nearly two-thirds of reductions in coarse particulate matter (PM10) and sulphur dioxide (SO2) from the United States have been reduced.