Reuters
The first of the reports, titled "Worldwide Cost of Living," looks at factors including food costs, fuel costs, and salaries.
And because of the strength of the US dollar and currency devaluations elsewhere, there have been a few major shifts in this year's rankings.
One of the editors of the survey, Jon Copestake, said: "In nearly 17 years of working on this survey I can't recall a year as volatile as 2015. Falling commodity prices have created deflationary pressures in some countries, but in others currency weakness caused by these falls has led to spiralling inflation."
Business Insider took a look at the nine most expensive cities in the world.