The Corruption Perceptions Index (CPI) is an index which ranks countries "by their perceived levels of public sector corruption, as determined by expert assessments and opinion surveys." The CPI generally defines corruption as an "abuse of entrusted power for private gain". The index is published annually by the non-governmental organisation Transparency International since 1995. The 2022 CPI, published in January 2023, currently ranks 180 countries "on a scale from 100 (very clean) to 0 (highly corrupt)" based on the situation between 1 May 2021 and 30 April 2022. Denmark, Finland, New Zealand, Norway, Singapore, and Sweden are perceived as the least corrupt nations in the world, ranking consistently high among international financial transparency, while the most apparently corrupt are Somalia (scoring 12), Syria and South Sudan (both scoring 13). Methods Transparency International commissioned the University of Passau's Johann Graf Lambsdorff to produce the CPI. The 2012 CPI takes into account 16 different surveys and assessments from 12 different institutions. The 13 surveys/assessments are either business people's opinion surveys or performance assessments from a group of analysts. Early CPIs used public opinion surveys. The institutions are: African Development Bank (based in Côte d'Ivoire) Bertelsmann Foundation (based in Germany) Economist Intelligence Unit (based in the UK) Freedom House (based in the US) Global Insight (based in the world) International Institute for Management Development (based in Switzerland) Political and Economic Risk Consultancy (based in Hong Kong) The PRS Group, Inc., (based in the US) World Bank World Economic Forum World Justice Project (based in US) Countries need to be evaluated by at least three sources to appear in the CPI. The CPI measures perception of corruption due to the difficulty of measuring absolute levels of corruption. Validity A study published in 2002 found a "very strong significant correlation" between the Corruption Perceptions Index and two other proxies for corruption: black market activity and an overabundance of regulation. All three metrics also had a highly significant correlation with the real gross domestic product per capita (RGDP/Cap); the Corruption Perceptions Index correlation with RGDP/Cap was the strongest, explaining over three-quarters of the variance. (Note that a lower rating on this scale reflects greater corruption so that countries with higher RGDPs generally had less corruption.) Alex Cobham of the Center for Global Development reported in 2013 that "many of the staff and chapters" at Transparency International, the publisher of the Corruption Perceptions Index, "protest internally" over