Rents go down, grocery bills shrink, companies lay off workers and people move away to live in the countryside - and yet somehow Tokyo continues to be the world's most expensive city for expatriates to live in.

Most of the blame can be placed firmly on the relentless strength of Japanese currency against the U.S. dollar, according to the annual cost of living survey by international human resources consulting firm, Mercer.

The capital shot back to top of the chart, swapping runner-up position with the Angolan capital of Luanda, which came first last year. Other Japanese cities - Osaka and Nagoya - also placed in the top 10. The results show that, all in all, Japan is one of the most expensive countries on earth for expats.

It's no wonder. Mercer's findings are based on "the relative strength of the relevant currency" against the U.S. dollar in the 12 months between rankings, as well as price fluctuations over the same period, using New York as a benchmark. The survey covers 214 cities across five continents. According to data from the Bank of Japan, the average dollar rate for the survey's most recent period through February 2012 was ¥78.9, an 8.6% decline from the previous year.