Mercer has just released its top 50 most expensive cities in the world based on cost of living.

Mercer’s Worldwide Cost of Living Survey 2008 is used to help multinational companies and governments determine living costs for their expatriate employees, who usually demand a relatively high quality of life.

Mercer’s survey covers 253 cities across six continents and measured the relative cost of over 200 items in each place, including housing, transport, food, clothing, household goods and entertainment.

For the third consecutive year, Moscow is the world’s most expensive city for expatriates.

Its position has been strengthened by the appreciation of the rouble against the US dollar and the continuous rising accommodation costs. 10 years ago Russia was in crisis !

Now, Moscow is home to 74 billionaires, the most of any city in the world.

Tokyo is in second position climbing two places since last year, whereas London drops one place to rank third. Oslo climbs six places to 4th place and is followed by Seoul in 5th.

“The decline in the ranking of all U.S. cities is due to the weakening value of the U.S. dollar against most major world currencies,” : New York (as the base city scoring 100 points) fell from No. 15 to No. 22. whereas several European cities have experienced a significant rise in the rankings this year.

The gap between the world’s most and least expensive cities now seems to be widening though. Find out more on Forbes.com