The preliminary International Comparison Program report on purchasing power parity -- or PPP -- was coordinated by the World Bank and based on price data on goods and services in 146 countries, adjusted to reflect local cost and affordability, and converted to dollars.

The report has no bearing on the actual size of those economies, but rather looks at them with a different measuring tool -- one that many emerging economies argue is a more accurate representation of their growing global influence since it takes their hefty buying power into account.

Many of those countries want the IMF to take PPP into consideration, when allocating voting rights, a contentious issue that is expected to be high on the agenda at the fund's spring meetings in April 2008.

An IMF spokesman said there was "growing consensus" that PPP should play a role in determining voting quotas, which would raise the relative weight of developing countries.

"The impact on individual countries depends on the data for them and this new set of PPP data will ensure that any calculations done for PPP purposes will reflect the most up-to-date situation," IMF's William Murray said in an e-mailed response to questions.

PPP is designed to provide an apples-to-apples comparison for the buying power of countries around the world, and also gives insight into the cost of living, consumer spending and investment from country to country.

One of the best-known examples is the "Big Mac Index," which compares the cost of the same McDonald's sandwich in different countries.

The report takes data collected by the World Bank, Eurostat and the Organization for Economic Cooperation and Development to calculate each country's PPP for 2005. (http://www.worldbank.org/data/icp)

China's share of the global economy in terms of PPP fell to 9.7 per cent from an estimated 14 per cent. This was the first time that China participated in the survey, so the prior figure was calculated last year by extrapolating from old data, using a model that has since proved to be faulty.

India's share of the world economy based on PPP dropped to 4.3 per cent from a previous estimate of 6 per cent. This was the first time India had participated in the survey since 1985.

"These are changes in estimates, the previous ones having been based on very old and very limited data," the ICP report noted. "The real outputs of their economies have not changed, only the way we measure them has."

Political Ramifications

When measured by market exchange rates instead of PPP, China's share of world GDP is just 5 per cent, and India's is less than 2 per cent -- about half of their size using PPP. That explains why the report may have political ramifications as fast-growing emerging markets fight for more say at the IMF.

Emerging markets argue that the big industrialized countries have too much influence over the fund, in part because voting rights do not take into account PPP -- something they hope will change in the IMF's revised quota system.

But because India and China are smaller than previously thought in PPP terms, they may have a harder time winning support for sizeable increases in their voting rights.

Some industrialized countries worry that China and other emerging markets will surpass them in voting power if PPP is taken into consideration. In PPP, China is the world's second- biggest economy, behind only the United States. By market exchange rates, it trails countries such as Japan and Germany.

The report shows that 12 countries account for more than two-thirds of the world's output, including five emerging economies: China, India, Russia, Brazil and Mexico.