IN THE spring of 2011 the Pew Global Attitudes Survey asked thousands of people worldwide which country they thought was the leading economic power. Half of the Chinese polled reckoned that America remains number one, twice as many as said “China”. Americans are no longer sure: 43% of US respondents answered “China”; only 38% thought America was still the top dog. The answer depends on which measure you pick. An analysis of 21 different indicators chosen by The Economist (see the full set) finds that China has already overtaken America on over half of them and will be top on virtually all of them within a decade.

Economic power is best gauged by looking at absolute size rather than per-person measures. On a few indicators, such as steel consumption, ownership of mobile phones and beer-guzzling (a crucial test of economic superiority), the milestone was reached as long as a decade ago. Several more have been passed since. In 2011 China exported about 30% more than the United States and spent some 40% more on fixed capital investment. China is the world's biggest manufacturer, and partly as a result it burns around 10% more energy and emits almost 40% more greenhouse gases than America (although its emissions per person are only one-third as big). The Chinese also buy more new cars each year than anybody else.

The country that invented the compass, gunpowder and printing is also challenging America in the innovation stakes. We estimate that in 2011 more patents were granted to residents in China than in America. The quality of some Chinese patents may be dubious but they will surely improve. The World Economic Forum's “World Competitiveness Report” ranks China 31st out of 142 countries on the quality of its maths and science education, well ahead of America's 51st place. China's external financial clout also beats America's hands down. It has total net foreign assets of $2 trillion; America has net debts of $2.5 trillion.

The chart shows our predictions for when China will overtake America on several other measures. Official figures show that China's consumer spending is currently only one-fifth of that in America (although that may be understated because of China's poor statistical coverage of services). Based on relative growth rates over the past five years it will remain smaller until 2023. Retail sales are catching up much faster, and could exceed America's by 2014. In that same year China also looks set to become the world's biggest importer—a huge turnaround from 2000, when America's imports were six times those of China.

 Find even more indicators and adjust the figures to make your own predictions using our interactive chart

What about GDP, the most widely used measure of economic power? The IMF predicts that China's GDP will surpass America's in 2016 if measured on a purchasing-power parity (PPP) basis, which adjusts for the fact that prices are lower in poorer countries. But America will only really be eclipsed when China's GDP outstrips it in dollar terms, converted at market-exchange rates.

In 2011 America's GDP was roughly twice as big as China's, down from eight times bigger in 2000. To predict how quickly that gap might be closed, The Economist has updated its interactive online chart (also here) which allows you to plug in your own assumptions about real GDP growth in China and America, inflation rates and the yuan's exchange rate against the dollar. Our best guess is that annual real GDP growth over the next decade averages 7.75% in China (down from 10.5% over the past decade) and 2.5% in America; that inflation (as measured by the GDP deflator) averages 4% and 1.5% respectively; and that the yuan appreciates by 3% a year. If so, then China will overtake America in 2018. That is a year earlier than our prediction in December 2010 because China's GDP in dollar terms increased by more than expected in 2011.

Second place is for winners

Even if China became the world's biggest economy by 2018, Americans would remain much richer, with a GDP per head four times that in China. But Rupert Hoogewerf, the founder of the annual Hurun Report on China's richest citizens, reckons that it may already have more billionaires. His latest survey identified 270 dollar billionaires but the true total, he says, is probably double that because many Chinese are secretive about their wealth. According to the Forbes rich list, America has 400 billionaires or so.

America still tops a few league tables by a wide margin. Its stockmarket capitalisation is four times bigger than China's and it has more than twice as many firms in the Fortune global 500, which lists the world's biggest companies by revenue. Last but not least, America spends five times as much on defence as China does, and even though China's defence budget is expanding faster, on recent growth rates America will remain top gun until 2025.

Being the biggest economy in the world does offer advantages. It helps to ensure military superiority and gives a country more say in fixing international rules. Historically, the biggest economy has become the issuer of the main reserve currency, which is why America has also been able to borrow more cheaply than it otherwise would. But it would be a mistake for American leaders to try to block China's rise. China's rapid growth benefits the whole global economy. It is better to be number two in a fast-growing world than top dog in a stagnant one.