The WTO was created in 1995 out of the Uruguay trade round to establish a set of rules for international trade negotiations. It has 153 member countries and functions to facilitate trade, formulate trade rules, protect developing countries' interests, and optimize resource use globally. Key principles of the WTO trading system include non-discriminatory trade, national treatment of imports, freer trade through negotiation, predictability through binding commitments and transparency, and fair competition and economic development. Trading blocs form different levels of trade agreements from free trade areas to full economic unions with common external tariffs and regulations.