WASHINGTON, Dec. 17 (Xinhua) -- The economies of China and India were much less than estimated when measured by purchasing power, the World Bank said Monday.

    The preliminary global report on "purchasing power parity" (PPP) provides estimates of internationally comparable price levels and the relative purchasing power of currencies for 146 economies, said a statement released by the World Bank.

    China participated in the survey program for the first time ever and India for the first time since 1985. The new results are more statistically reliable estimates of the size and price levels of both economies, according to the Bank.

    Under the old calculation, China had a GDP of 8.8 trillion dollars in 2005, about 15 percent of global GDP of 59 trillion dollars, while according to the new measure, China's economy shrank by 40 percent to 5.3 trillion dollars, which is about 10 percent of global GDP of 55 trillion dollars.

    India's share of the world economy based on PPP dropped to 4.3 percent from a pervious estimate of 6 percent.

    Overall, the 2005 benchmark results show that the size of the world economy measured in PPP terms is smaller than previous estimates. The Asian and African economies are one-third and one-fourth smaller, respectively.

    However, Asia still accounts for over 20 percent of the world's output.

    In the study, the United States still has the world's biggest economy with 23 percent of global output. That compares with 29 percent using market rates.

    The most expensive economies are Iceland, Denmark, Switzerland, Norway, and Ireland with the Price Level Index (PLI) ranging from 154 to 127. The United States ranked 20th in the world, lower than most other high-income economies, including France, Germany, Japan and Britain, according to the report.

    The PLI shows which economies are the most and least expensive. It corresponds to travelers' experience of making purchases after converting their currency at market exchange rates

    An index over 100 means prices are higher on average than in the U.S., and one less than 100 means prices are relatively lower.

    The cheapest economy in the world are Tajikistan, followed by Ethiopia, Gambia, Kyrgyzstan and Bolivia, the report added.