A second approach to answer the question is to examine the development in economic growth of countries that abandon trade barriers. Here, the assumption that interaction with other countries leads to prosperity fares well, too. A typical result of countries opening up to the global economy is an increase in economic growth (Mankiw, 2010: 229). To give an example, the GDP of countries in East Asia and the Pacific has – as reported by the World Bank -- increased significantly since they started to pursue outward-oriented developing strategies, while at the same time, poverty has been reduced.4.
With regard to these findings, one might argue that trade is indeed a "positive-sum" game as it furthers economic growth of the countries involved. However, it is questionable whether the data provided by international organizations like the WTO really serves as a proof for liberal claims. One has to consider that the Western-dominated international organizations providing data on the issue and promoting international free trade to countries worldwide tend to be biased toward mutual exchange and hence ignore the tentative and fragile nature of their findings (Ravenhill, 2014: 314).
Moreover, the findings appear to be consistent with liberal claims, but they are not conclusive as correlation does not imply causation (Mankiw, 2010: 229) and the evidence looks ambiguous when examined more closely. For instance, the effect of open trade on a country's prosperity is often measured by changes in the ratio of trade to GDP. However, studies analyzing this relationship have found that it is not a strong one (Ravenhill, 2014: 314).
Contrary to liberal claims, the single robust relationship derived from the data is that states reduce trade barriers when their economy becomes wealthier – and most of the countries (including the US) that are now rich and promoting free trade had indeed high trade barriers during their period of fast growth (Ravenhill, 2014: 314).
