<P> NAFTA has two supplements: the North American Agreement on Environmental Cooperation (NAAEC) and the North American Agreement on Labor Cooperation (NAALC). </P> <P> Most economic analyses indicate that NAFTA has been beneficial to the North American economies and the average citizen, but harmed a small minority of workers in industries exposed to trade competition . Economists hold that withdrawing from NAFTA or renegotiating NAFTA in a way that reestablishes trade barriers will adversely affect the U.S. economy and cost jobs . </P> <P> Following diplomatic negotiations dating back to 1990 among the three nations, U.S. President George H.W. Bush, Canadian Prime Minister Brian Mulroney and Mexican President Carlos Salinas signed the agreement in their respective capitals on December 17, 1992 . The signed agreement was then ratified by each nation's legislative or parliamentary branch . </P> <P> The earlier Canada--United States Free Trade Agreement had been controversial and divisive in Canada, and the 1988 Canadian election involved discussion on the issue . In that election, more Canadians voted for anti-free trade parties (the Liberals and the New Democrats) but the split caused more seats in parliament to be won by the pro-free trade Progressive Conservatives (PCs). Mulroney and the PCs had a parliamentary majority and were easily able to pass the 1987 Canada - U.S. FTA and NAFTA bills . However, he was replaced as Conservative leader and prime minister by Kim Campbell . Campbell led the PC party into the 1993 election where they were decimated by the Liberal Party under Jean Chrétien, who had campaigned on a promise to renegotiate or abrogate NAFTA; however, Chrétien subsequently negotiated two supplemental agreements with the new U.S. president . In the U.S., Bush, who had worked to "fast track" the signing prior to the end of his term, ran out of time and had to pass the required ratification and signing of the implementation law to incoming president Bill Clinton . Prior to sending it to the United States Senate Clinton added two side agreements, The North American Agreement on Labor Cooperation (NAALC) and the North American Agreement on Environmental Cooperation (NAAEC), to protect workers and the environment, plus allay the concerns of many House members . It also required U.S. partners to adhere to environmental practices and regulations similar to its own . </P>

When was the north american free trade agreement signed