Trends in trade have also been fueled by lowering of supply chain costs and an increase in preferential trade agreements. Since the 1930s, these trends have also been fueled by a lowering of costs for sea freight and passenger air transport.40 Looking at trade agreements shows a slow increase from 1950–1977 to fifty agreements, holding steady with only modest increases from 1977–1990, an exponential rise to more than 280 agreements by 2000, and then a leveling off until 2010 at the end of the data set.
