The North American Free Trade Agreement (NAFTA) entered into force on January 1, 1994. The agreement was signed by President George H.W. Bush on December 17, 1992, and approved by Congress on November 20, 1993. The NAFTA Implementation Act was signed into law by President William J. Clinton on December 8, 1993 (P.L. 103-182). The overall economic impact of NAFTA is difficult to measure since trade and investment trends are influenced by numerous other economic variables, such as economic growth, inflation, and currency fluctuations. The agreement may have accelerated the trade liberalization that was already taking place, but many of these changes may have taken place with or without an agreement. Nevertheless, NAFTA is significant because it was the most comprehensive free trade agreement (FTA) negotiated at the time and contained several groundbreaking provisions. A legacy of the agreement is that it has served as a template or model for the new generation of FTAs that the United States later negotiated and it also served as a template for certain provisions in multilateral trade negotiations as part of the Uruguay Round.