Tokyo is the world’s most expensive city, according to Mercer’s 2009 Worldwide Cost of Living survey released today, with the cost of living up 13.1% from 2008.

Japan’s capital is followed by Osaka and Moscow, which held the top spot in last year’s rankings. Geneva comes in fourth.

The significant changes from last year are due to massive swings in exchange rates, with many currencies at their weakest in years against the U.S. dollar, during the March 2009 survey period.

Because of this, New York moved up 14 spaces to No. 8 from No. 22. London dropped to No. 16 from No. 3 as the pound dropped as low as 1.37 against the U.S. dollar during the study period.

Six months earlier, one pound was worth $1.86.

Some cities fell dramatically in the rankings. Warsaw was down 78 places from 35th to 113th. Sydney has dropped 51 places from 15th to 66th and Mumbai went from 48th place to 66th.

Source: Forbes