Since 1995, Transparency International

Transparency International

Transparency International is a non-governmental organization that monitors and publicizes corporate and political corruption in international development. It publishes an annual Corruption Perceptions Index, a comparative listing of corruption worldwide...

 (TI) publishes the Corruption Perceptions Index (CPI) annually ranking countries "by their perceived levels of corruption, as determined by expert assessments and opinion surveys." The CPI generally defines corruption

Political corruption

Political corruption is the use of legislated powers by government officials for illegitimate private gain. Misuse of government power for other purposes, such as repression of political opponents and general police brutality, is not considered political corruption. Neither are illegal acts by...

 as "the misuse of public power for private benefit." , the CPI ranks 178 countries "on a scale from 10 (very clean) to 0 (highly corrupt)."
Transparency International commissioned Johann Graf Lambsdorff of the University of Passau

University of Passau

The University of Passau is a public research university located in Passau, Lower Bavaria, Germany. Founded in 1978, it is the youngest university in Bavaria and has therefore the most modern campus in the state...

 to produce the Corruption Perceptions Index (CPI).