Note: In 1990 Dollars, purchasing power parity.
Source: Data compiled by A. Maddison, University of Groningen. Updated with World Bank GDP figures for 2010.
Share of the World's GDP, 1AD - 2010
Historically, the world's balance of wealth (power) undertook two major shifts, one triggered by the industrial revolution (early 19th century) and the other, unfolding, triggered by globalization (late 20th century). Prior to the industrial revolution, the economic size of a nation was directly proportional to its population, which was dominantly rural. Agricultural surpluses permitted an initial division of labor and was used to support various crafts, administrative and service activities. The capacity to grow food was therefore the foundation of the wealth of nations because the greater the food surplus the larger the population base for non-agricultural activities. Since China and India were mostly relying on rice cultivation (the most productive form of agriculture) supported by extensive irrigation systems, they achieved early in history the world's largest populations and correspondingly the largest GDP. They jointly accounted for 50% of the world's GDP up to the early 19th century.
The mechanization of production brought by the industrial revolution significantly changed the relationship between population and economic output. European countries and their offshoots (e.g. the United States), which historically had a modest share of the global GPD (the Roman Empire being a notable exception), were able to become the world's dominant economies, some projecting this influence through colonial empires. By 1900, five nations accounted for about 45% of the world's GPD (United States, Great Britain, Germany, France, Italy and Japan), with the share of China and India collapsing to less than 20%. By the 1970s, China and India jointly accounted for less than 9% of the world's GDP in spite of their surging populations while the share of the United States peaked at 22% of the world's GDP.
In the late 1980s and early 1990s a rebalancing of the world's GDP began. By undertaking their own industrial revolution within an integrated global economy, China and later India, were able to gradually reclaim a share of the GDP more in line with their populations. It could be postulated that once this rebalancing is completed, the global economy will reach a new equilibrium where economic output will be correlated with population, as it is was before the industrial revolution. This assumes an eventual homogeneity of standards of living and income across the global population, which may not occur.