The cost of living in Istanbul has fallen sharply over the last year, taking the city to 70th place in a list of most expensive cities around the world, down from 44th, according to Mercer, a global human resources consulting company.

Luanda of oil-rich Angola secured its top spot in the “2011 Cost of Living” list by Mercer, which evaluated 214 cities on six continents in terms of living conditions for expatriates.

More than 200 criteria used in the evaluation included housing, transportation, food, clothes, house goods and entertainment.

Japan’s capital, Tokyo, and N’Djamena of Chad followed Luanda on this year’s list. Osaka, another Japanese city, ranked sixth.

The cheapest city, according to the survey, was Pakistan’s financial center Karachi, where the cost of living was three times cheaper than in Luanda.

It also said natural disasters and political and social uprisings in the Middle East have deeply affected the living conditions of expatriates in the region.

In some cities, it is only practical for an expat to live in an enclave because of crime and the availability of modern services, the survey said.