Interior of a large sanitary sewer viewed from an access manhole. In the developed world, sewers are pipes from buildings to one or more levels of larger underground trunk mains, which transport the sewage to sewage treatment facilities.
Free trade is a policy followed by some international markets in which countries' governments do not restrict imports from, or exports to, other countries. Free trade is exemplified by the European Economic Area and the North American Free Trade Agreement, which have established open markets. Most nations are today members of the World Trade Organization (WTO) multilateral trade agreements.
The North American Free Trade Agreement (NAFTA) is a treaty entered into by the United States, Canada, and Mexico; it went into effect on January 1, 1994.Most of the studies of NAFTA concentrate on the effects of U.S. business with Mexico. Trade with Canada has also been enhanced, but the passage of the trade agreement did not have as great an impact on the already liberal trade practices that America and its northern neighbor abided by.).