Transparency International has changed the formulation for how they estimate corruption perception index (CPI). The old formulation has data from 1995 - 2011. The new data begins in 2012.
Among Transparency International’s published documents, two indexes are frequently used in the academic arena: TI Bribe Payers Index and Corruption Perceptions Index.
The TI Bribe Payers Surveys are comprehensive studies on bribe-paying in international trade covering unfair business practices, assesses the readiness of the private sector for the new ban on bribing foreign public officials. The TI Corruption Perceptions Index (CPI) ranks countries in terms of the degree to which corruption is perceived to exist among public officials and politicians. The CPI conducts surveys on the misuse of public power for private benefit, with a focus, for example, on bribe-taking by public officials in public procurement.
The TI Corruption Perceptions Index (CPI), 2008 ranks 180 countries in terms of the degree to which corruption is perceived to exist among public officials and politicians. It is a composite index, drawing on 17 different polls and surveys from 13 independent institutions carried out among business people and country analysts, including surveys of residents, both local and expatriate. This composite index ranging between 100 (highly clean) and 0 (highly corrupt) indicates the perceptions of the degree of corruption as seen by business people, academics and risk analysts. The TI indexes are freely available at TI’s website: http://www.transparency.org.