The United States is in long-term relative decline. In absolute terms, the America of the future will be richer. But because other countries like China and India, and other regions like Africa, are growing more rapidly, America’s share of global wealth will decline. So will America’s share of global military power, which, in the industrial era, is loosely rather than perfectly correlated with relative economic weight.

Primacy, as a concept in international relations, can refer either to polarity (a country’s share of global economic and military resources) or to hegemony (a specialized function within an interdependent international community). Whether defined as polarity or hegemony, American global primacy is coming to an end.

Projections of national shares in GDP in 2050 by think tanks, investment banks and consulting firms tend to converge at the prediction that the world will have three economic poles or cores—China, the United States and Europe—or perhaps four, if India enjoys rapid and sustainable growth. “The World in 2050,” a report by PwC, assigns 20 percent of global GDP (in purchasing power parity) to China, 14 percent to the United States and India, and a mere 12 percent to Europe as a whole in 2050. A 2015 report by the Economist Intelligence Unit paints a similar picture, concluding: “By 2030 the top three economies of the world will be the US, China and India. Such will be the growth of the two latter countries, in particular, that by 2050 they will each be richer than the next five (Indonesia, Germany, Japan, Brazil, and the UK) put together. This will represent a scale of wealth relative to the rest of the top ten that is unique in recorded history.” Indeed, to use PwC’s numbers, China, the United States, India and Europe together would account for around 60 percent of global GDP. Sub-Saharan Africa’s population will explode in the next few generations, but its successful development, if it occurs, will take a long time.

The “Brexit” vote in the UK, together with the growth of nationalism and populism in Europe, has doomed the elite project of creating a federal Europe that can act as a superpower in world politics. Europe will be a rich but fragmented trading bloc surrounded by colossal continental powers, the United States, China and perhaps India.

Tomorrow’s world will be multipolar, not simply bipolar or tripolar. The rise of China and India to great-power status will allow regional powers, from Turkey to Vietnam and Brazil, to play the continent-states against one another and pursue their own independent interests.

The period between 1914 and 2014 can accurately be described as “the American century.” At some point during World War I, the gross domestic product of the United States passed that of the British Empire as a whole. Around a century later in 2014, according to the IMF, the GDP of China passed that of the United States.

After a hundred years in which it typically enjoyed a huge advantage in wealth and power over the next nearest competitors, with China the United States may finally have met a true “peer competitor.” Although per capita income in China is still much lower than in the United States, China is not only the world’s largest economy in terms of purchasing power parity (PPP), but also the world’s largest manufacturing nation—producing 52 percent of color televisions, 75 percent of mobile phones and 87 percent of the world’s personal computers. The Chinese automobile industry is the world’s largest, twice the size of America’s. China leads the world in foreign exchange reserves. The United States is the main trading partner for seventy-six countries. China is the main trading partner for 124. With growing wealth comes growing power. China is now second only to the United States in its defense spending.

For the first time since it surpassed the British Empire in the early 1900s, the United States faces a rival that, though poorer in per capita terms and still inferior in many ways, has an economy equal in scale to its own. This is a new development. America’s earlier challengers, Germany and the Soviet Union, were nowhere near the United States in their size and resources. Other nations, like Japan, were even less able to challenge U.S. economic and potential military primacy (which began with World War I), or U.S. international institutional hegemony (which began during and continued after World War II).

John Maynard Keynes observed: “The great events of history are often due to secular changes in the growth of population and other fundamental economic causes, which escaping by their gradual character the notice of contemporary observers, are attributed to the follies of statesmen.” The increasing frustrations in U.S. foreign policy have less to do with the failures of American leaders than with deep, long-term trends that are diffusing both wealth and power away from both the United States and Europe.

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