High rents aren't just a problem in the U.S. A new study from RentCafé showed the most unaffordable cities in the world to rent in, based on median income.

The study used PricewaterhouseCoopers’ ranking of the world’s Cities of Opportunity, an in-depth analysis of the most prosperous global business, finance and culture capitals. The study looks at 10 different indicators including infrastructure, intellectual capital and innovation, sustainability and ease of doing business.

Of the 30 cities on the list, Manhattan is the priciest city in the world in which to rent, and its population pays an average of 59% of their income in rent.

In San Francisco, the median income sits at about $92,000, one of the highest income levels represented, but that's still not enough to keep with the rising rent prices. The rent-to-income ratio stands at about 41% in San Francisco.

Here are the top five least affordable cities in the world and their rent-to-income rations:

5. Paris – 46%

Rent per month: $1,600

Household income per month: $3,442

4. Los Angeles – 47%

Rent per month: $2,055

Household income per month: $4,333

3. Lagos, Portugal – 57%

Rent per month: $355

Household income per month: $625

2. Manhattan – 59%

Rent per month: $3,725

Household income per month: $6,298

1. Mexico City – 60%

Rent per month: $720

Household income per month: $1,208