Corruption Perceptions Index 2021

METHODOLOGY The CPI aggregates data from a number of different sources that provide perceptions among business people and country experts of the level of corruption in the public sector. The following steps are taken to calculate the CPI: 1. Select data sources. Each data source used to construct the CPI must fulfil the following criteria to qualify as a valid source: + Quantifies risks or perceptions of corruption in the public sector + Is based on a reliable and valid methodology + Comes from a reputable organisation + Allows for sufficient variation of scores to distinguish between countries + Ranks a substantial number of countries + Considers only the assessments of country experts or business people + Is regularly updated. The CPI 2021 is calculated using 13 different data sources from 12 different institutions that capture perceptions of corruption within the past two years. 2. Standardise data sources to a scale of 0-100. This standardisation is done by subtracting the mean of each source in the baseline year from each country score, then dividing by the standard deviation of that source in the baseline year. This subtraction and division using the baseline year parameters ensures that the CPI scores are comparable year on year since 2012. After this procedure, the standardised scores are transformed to the CPI scale by multiplying them with the value of the CPI standard deviation in 2012 (20) and adding the mean of the CPI in 2012 (45), so that the dataset fits the CPI’s 0-100 scale. 3. Calculate the average. For a country or territory to be included in the CPI, a minimum of three sources must assess that country. A country’s CPI score is then calculated as the average of all standardised scores available for that country. Scores are rounded to whole numbers. 4. Report the measure of uncertainty. The CPI score is accompanied by a standard error and confidence interval. This captures the variation across the data sources available for a country or territory. CORRUPTION PERCEPTIONS INDEX 2021 15