The cooperative approach towards trade, which is reflected in Asian International Input-Output tables, is the main factor influencing East Asian economic development. In this research, we have calculated interdependency and self-sufficiency indicators by using recently published IIO 2005. We also have used Shrestha and Hasebe (2006) results for 1990, 1995, 2000 to analyze the trends of the indicators. The results show that the interdependency has increased in the region during 1990-2005, but it has decreased in other countries in the world. The interesting result is that despite the gradual decline in self-dependency indicators of the East Asian countries during 1990-2005, they are still high in 2005. It means that the trade policy in the last three decades has been focused on importing only intermediate goods instead of final goods in order to increase the internal capacity of production. These changes have been analyzed by three phases of East Asian regionalism (Baldwin, 2008); (a) rampant unilateralism, (b) regionalism delayed, unilateralism accelerated, and (c) rampant regionalism. Due to the importance of Japan and China in the region, the trade interdependencies between countries with respect to Japan and China are also calculated separately. The results show decreasing interdependency of those countries to Japan, but increasing to China since 2000.