<P> In world systems theory, the core countries are the industrialized capitalist countries on which periphery countries and semi-periphery countries depend . Core countries control and benefit from the global market . They are usually recognized as wealthy nations with a wide variety of resources and are in a favorable location compared to other states . They have strong state institutions, a powerful military and powerful global political alliances . </P> <P> Core countries do not always stay core permanently . Throughout history, core nations have been changing and new ones have been added to the core list . The most influential countries in the past have been what would be considered core . These were the Asian, Indian and Middle Eastern empires in the ages up to the 16th century, prominently India and China were the richest regions in the world until the 15th century, when the European powers took the lead, although the major Asian powers such as China were still very influential in the region . Europe remained ahead of the pack until the 20th century, when the two World Wars turned disastrous for the European economies . It is then that the victorious United States and Soviet Union, up to late 1980s, became the two hegemons, creating a bipolar world order . The heart of civilisation consists of Western Europe, North America, Australasia and Japan . The population of the core is by far the wealthiest and best educated on the planet . </P> <P> Core countries control and profit the most from the world system, and thus they are the "core" of the world system . These countries possess the ability to exercise control over other countries or groups of countries with several kinds of power such as military, economic, and political power . </P>

When did the usa join the core of the modern world system