This question shows which goods of the countries are subject to customs duties at this preferential rate. The boundary between a PTA and a free trade area (PTA) can blur, with almost all PTAs having the main objective of becoming a free trade agreement under the General Agreement on Tariffs and Trade. With the recent proliferation of bilateral PTAs and the emergence of mega-TAPs (broad regional trade agreements such as the Transatlantic Trade and Investment Partnership (TTIP) or the Trans-Pacific Partnership (TPP), a global trading system managed exclusively within the framework of the WTO seems unrealistic and interactions between trading systems must be taken into account.