Any rating below 50 is considered more corrupt than clean.
Five European Union member states earned scores below 50, including Italy, Greece, Romania, Slovakia and the Czech Republic.
Notwithstanding the occasional crack-smoking mayor, Canada also outranks the U.S. with a score of 81.
(Read more: 10 corruption hot spots)
Countries that improved their standings on the index this year include Myanmar, Brunei, Lesotho, Senegal, Nepal, Estonia and Latvia.
Others that have lost ground this year include high-ranking Australia, Slovenia and Iceland, as well as Spain, the Gambia, Guinea-Bissau, Libya, Mali, Eritrea, Mauritius, Yemen, Guatemala, Madagascar and Congo Republic.
The index, of course, is not without its limitations. It measures only about half of the 322 countries around the globe and focuses only on corruption in the public sector (government agencies, justice system, etc.).
Transparency International warns that countries ranking at the bottom of the index are not necessarily the most corrupt societies overall.
(Read more: What's the solution to chronic Greek corruption?)
"Corruption remains notoriously difficult to investigate and prosecute" and will likely stymie efforts to tackle international scourges such as extreme poverty, climate change and economic crisis, Transparency International said in a press release.
The group calls on international bodies such as the G20 to "crack down on money laundering, make corporations more transparent and pursue the return of stolen assets."