The North American Free Trade Agreement is an agreement signed by Canada, Mexico, and the United States, creating a trilateral rules-based trade bloc in North America. The agreement came into force on January 1, 1994. It superseded the Canada–United States Free Trade Agreement between the U.S. and Canada. NAFTA has two supplements: the North American Agreement on Environmental Cooperation and the North American Agreement on Labor Cooperation. In terms of combined purchasing power parity GDP of its members, as of 2013 the trade bloc is the largest in the world as well as by nominal GDP comparison.