Professor Frankel acknowledged in a telephone interview on Thursday that the new World Bank figures badly damaged that argument. “I would have to retract that based on these latest numbers,” he said.

But Professor Frankel said that many other economic indicators showed that the yuan was undervalued and should be allowed to rise.

He cited China’s huge and growing trade surplus, its ever-rising foreign exchange reserves, market speculation on a further appreciation of the yuan  it has already risen 5.9 percent this year  and signs that the Chinese economy might be overheating as exports soared.

Some economists, including the former head of the China division at the International Monetary Fund, question whether the World Bank has now gone too far in the other direction and overstated prices in China. While describing the estimates as an important step toward making international comparisons of economies, they point out that the bank looked mainly at affluent Chinese cities in coastal provinces with big export industries.

China’s economic output in 2005 was worth $2.24 trillion at prevailing prices and actual market exchange rates. That is the calculation most commonly used by economists and the best indicator of a country’s ability to buy and sell a diverse range of internationally traded products, like oil, steel and computers.

The World Bank had previously calculated that China’s output was worth $8.8 trillion in 2005 if the goods and services produced in the country were valued at American prices. That figure was revised this week down to $5.3 trillion.

The bank found that prices in China were closer to world levels than it previously assumed. So World Bank economists calculated that the purchasing-power parity of China’s economy was also closer to the market exchange value. Even with the revision, China is still the world’s second-largest economy in purchasing-power-parity terms, after the United States. At market exchange rates, China also trails Japan.