The North American Free Trade Agreement (NAFTA) is a treaty between the United States, Canada and Mexico; it entered into force on 1 January 1994. (Free trade between the United States and Canada has existed since 1989; NAFTA extended this agreement.) On that day, the three countries became the largest free market in the world – the combined economies of the three countries at the time were $6 trillion and directly affected more than 365 million people. NAFTA was created to eliminate tariff barriers to agriculture, production and services; removal of investment restrictions; and to protect intellectual property rights. This should be done taking into account environmental and labour concerns (although many observers have been negligent in ensuring environmental and occupational health and safety measures since the entry into force of the agreement). .