At the end of the 20th century, the WTO was attacked by environmentalists, trade unions and proponents of sustainable development in many countries, because the organization was able to repeal national protection laws when they were seen as an obstacle to free trade, and because critics argued that the WTO was promoting an international economic system that favoured rich countries and large private companies at the expense of the poor. Ministerial conferences have often been the scene of open-air public events and clashes between the poorest third world countries and the most prosperous industrialized countries. Together with the major international credit agencies – the World Bank and the International Monetary Fund – the WTO has been forced to defend the impartiality of a policy to support global economic growth. The gravitational equation has become the most important econometric approach for the ex-post study of the «partial» (or direct) impact of economic integration agreements on bilateral trade flows as a whole. After taking into account multilateral resistance conditions, with fixed effects that alter time and control of endogenous distortion using panel data techniques ,  find that free trade agreements significantly increase countries` bilateral trade flows using five-year data from 1960 to 2000 for 96 countries. After this empirical strategy and the same set of data,  goes even further by comparing the effects of North-South and South-South trade agreements on bilateral trade and showing that free trade agreements lead to an increase in bilateral trade, whether the signatory countries are developing or industrialized countries. In particular, they note that the percentage increase in bilateral trade is higher in the South-South agreements than in the North-South agreements. The U.S. State Department also found good use of free trade expansion after World War II. Many in the Department of Foreign Affairs saw multilateral trade agreements as a means of integrating the world in accordance with the Marshall Plan and the Monroe Doctrine. U.S. trade policy has become an integral part of U.S. foreign policy.
This search for free trade as diplomacy intensified during the Cold War, when the United States competed with the Soviet Union for relations around the world.  The next natural step is to divide the fake PTA taking into account the group to which each trading partner belongs (Column 4). The results indicate that preferential trade agreements have a positive impact in all four cases. The most significant effect is trade flows between industrialized countries (0.3984), while point estimates for the other three combinations range from 0.111 to 0.248.