Hong Kong has overtaken Angola's capital to become the costliest city in the world for expats, Mercer's annual survey said Wednesday.

After topping the Cost of Living report for three consecutive years, Luanda was pipped by the Asian city in 2016, owing to a stronger Hong Kong dollar.

The survey by the Mercer consulting group compares the cost of over 200 items in over 200 cities, including housing, food, transport and entertainment.

It takes New York as its base for comparison and measures currency movements against the dollar, which has appreciated significantly over the past year. The Hong Kong dollar is pegged to the greenback.

"Generally speaking, prices remained stable across the world," Bruno Rocquemont of Mercer France told AFP, attributing steep rises or falls in cities' rankings chiefly to exchange rate fluctuations.

A strong yen propelled Tokyo six places higher to become the world's fifth-most expensive expat destination, behind Zurich and Singapore in third and fourth place respectively.

The cost of living in several US cities also rose on the back of the strong dollar.

Conversely, cities in countries whose currencies have slumped became more affordable, with Moscow recording one of the most spectacular price slides, falling from 17th costliest city for expats to 67th.

Bottom of the table of 209 cities was Namibia's capital Windhoek.

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