The idea that international trade is the engine of economic growth goes back to the times of Adam Smith. However, its popularity subsided around the 1950s, 1960s and 1970s in favour of 20th century protectionist theories, especially in developing countries where Import Substitution Industrialisation (ISI) strategies were implemented. Persistent, independent academic research during the reign of the protectionist paradigm rejuvenated support for more open and outwards-oriented trade. Gradually, in the 1980s, protectionist theory yielded its hold on economic advisors and politicians. Behind this change of paradigm was the widespread debt crisis in 1982 among ISI followers, and the collapse of communism in central and Eastern Europe.