中国经济不象原来想象中的那么大

Economics focus

中国经济不象原来想象中的那么大

A less fiery dragon?

China may be a smaller economic giant than previously thought

Nov 29th 2007

From The Economist print edition

AMERICANS who spend their time fretting about when their economy will be overtaken by China will have gleefully leapt upon new numbers suggesting that China's economy may in fact be 40% smaller than current estimates. However, the new figures, if confirmed, would also mean that the world economy has been growing rather more slowly in recent years than officially reported by the IMF, which is less salutary for everyone.

It is not the Chinese government that has been exaggerating the size of its GDP, but international organisations, such as the World Bank and the IMF, which measure each nation's output in terms of purchasing-power parity (PPP). If China's GDP is converted into dollars using market exchange rates it amounted to $2.7 trillion last year, only one-fifth of America's $13.2 trillion, and the fourth-largest in the world. But a dollar buys a lot more in China than in America because prices of many non-traded goods and services tend to be much lower in poor economies. Converting a poor country's GDP into dollars at market exchange rates therefore understates the true size of its economy.

Instead many economists prefer to convert GDPs into dollars using PPPs, which take account of price differences between countries. The Economist's Big Mac index is a crude measure of PPP. Much more sophisticated estimates are produced by the International Comparison Programme, co-ordinated by the World Bank, which gathers prices for more than 800 goods and services in countries around the globe. On a PPP basis, the World Bank ranks China as the world's second-biggest economy, with a GDP of $10 trillion last year. At its recent pace of growth, China's GDP could overtake America's by 2010.

The World Bank's estimate for China is widely used by economists. Yet few realise that it is based on a lot of guesswork, as the bank's previous international price surveys have not included China. Instead, it extrapolated from a study of prices in America and China that dates all the way back to the 1980s. The bank's latest price-comparison study, due to be published in mid-December, does include China for the first time, and preliminary evidence indicates that its GDP has been overstated in the past. In a recent article in the Financial Times, Albert Keidel, an economist at the Carnegie Endowment for International Peace, noted that PPP figures published by the Asian Development Bank (ADB), as part of its input into the World Bank's International Comparison Programme, implied that China's GDP was 40% smaller than the number reported by the World Bank. Interestingly, the new figure is very close to what the Big Mac index has indicated all along.

Mr Keidel's claim is itself based on some guesswork. The ADB report does not actually reveal the yuan's revised PPP rate against the dollar, as it only compares prices with those in Hong Kong, not America. To derive dollar PPPs Mr Keidel has assumed that relative prices in Hong Kong and America have not changed since previous studies. If this holds, then China's implied GDP is indeed 40% smaller than before. The World Bank says that it is still discussing the final numbers. Note, however, that the ADB figures imply that India's GDP is also now 40% smaller, even though India has taken part in previous international pricing surveys (suggesting that Hong Kong's PPP may in fact have changed). It is thus possible that China's GDP may be trimmed by less than 40% when the World Bank publishes its final report.

Assume for a moment that Mr Keidel's figure of 40% is correct, then China's GDP in PPP terms is slashed from $10 trillion to $6 trillion. That would still leave it as the world's second-largest economy, but it would not overtake America for at least another ten years. India, on the other hand, would drop from third to fifth place in the world ranking.

Adjusting the global speedometer

China would probably be quite happy to see its GDP revised down, hoping that America might stop picking on a smaller, poorer economy. But revised PPPs would not only change international rankings, they would also affect the pace of global growth. To calculate world GDP growth, individual countries' growth rates are weighted by their share of world output. Using PPP weights, as the IMF does, the world economy has grown by an average of 5% over the past five years, its strongest pace since the early 1970s. This is largely because emerging economies have been growing by 7.5% a year (compared with only 2.3% in the G7 developed economies), and they account for around half of world GDP. But if China and India are 40% smaller than previously thought, world growth would be trimmed to 4.5%.

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The difficulty of measuring PPP is one reason why some economists prefer to compare the sizes of economies using market exchange rates. After all, it is argued, countries trade with each other at market rates, so these provide the best basis for comparison. Measured this way, world growth over the past five years has been a still more modest 3.4%. Far from being the fastest pace for decades, that is slower than in the 1980s (see left-hand chart). So has the global boom been a mirage? A closer look at the numbers shows that this cannot be right. Measured at market exchange rates, emerging economies' share of global output last year was less than in 1980 (see right-hand chart), even though they have been growing more than twice as fast as the rich economies. The increase in their share of global energy consumption, from 43% in 1980 to 55% in 2006, also confirms that their weight in the world economy has surely risen.

The raw dollar numbers are distorted by big currency swings. For instance, the devaluations in East Asian economies in 1997-98 grossly exaggerated the drop in their output. Measured at PPP, emerging economies' share of world output has more realistically risen since 1980?and even if China's economy is smaller than thought, it is still a mighty beast. PPP data may be imperfect, but they give a better picture of the relative size of economies than market exchange rates do. In the words of John Maynard Keynes, ?It is better to be roughly right than precisely wrong.?