Protesters calling for Zimbabwean President Robert Mugabe to step down cheer in front of a military vehicle in Harare, Zimbabwe, in November 2017. REUTERS/Philimon Bulawayo The World Economic Forum on Tuesday released its annual corruption index as part of its "Global Competitiveness Report."

Using a methodology linked to Transparency International's Corruption Perception Index, the WEF ranked 140 countries' level of corruption within their society on a scale of one to 100.

A score of 100 means a country is without corruption, while zero is the most corrupt possible. All the countries featured on this list scored 30 or less.

The countries the WEF views as most corrupt tend to be in Africa, Central America, and the Middle East, in societies with weak legal and governmental systems and widespread poverty.

For instance, the WEF ranked Yemen, which is in the middle of a brutal civil war, as the most corrupt nation. But a handful of the world's 20 largest economies also made it onto the list.

Check out the world's most corrupt nations below.