In this article, we explore why oil import patterns differ between states with a view to understanding the relationship between agent-based explanations such as strategy and structural explanations—for example, geography. We compare degree of diversification between China and Japan in an effort to explore the relationship between agency and structure in the formation of energy security policy. The China-Japan comparison is contextualized with reference to the baseline case of the United States, a well-diversified importer. We employ the Shannon-Wiener index of diversity to assess the extent of oil import diversification, and temporal changes in diversification for China, Japan, and the United States. A key finding is that China's statist approach has allowed it to diversify its sources of imported oil more quickly than Japan's hybrid approach. In fact, since becoming a net oil importer in 1993, China's sources of imported oil have diversified quite rapidly. Japan's overreliance on the Middle East for much of its imported oil has been endemic since 1973.
