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The ABCs of the CPI: How the Corruption Perceptions Index is calculated

Got questions about our flagship Corruption Perceptions Index? We have you covered.

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The Corruption Perceptions Index (CPI) is the most widely-used global corruption ranking in the world. It measures how corrupt each country’s public sector is perceived to be, according to experts and businesspeople.

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The Corruption Perceptions Index explained.

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How do 180 countries & territories perform on the 2021 CPI?

2021

How are country scores calculated?

Each country’s score is a combination of at least 3 data sources drawn from 13 different corruption surveys and assessments. These data sources are collected by a variety of reputable institutions, including the World Bank and the World Economic Forum.

CPI scores do not reflect the views of Transparency International or our staff.

The CPI is the leading measurement for public sector corruption worldwide. Because it combines many different manifestations of corruption into one globally comparable indicator, it provides a more comprehensive picture of the situation in a particular country than each source taken separately. The process for calculating the CPI is regularly reviewed to make sure it is as robust and coherent as possible. This was done most recently by the European Commission’s Joint Research Centre in 2017.

For more details about the data sources, the type of respondents and the specific questions asked, download the full information pack.

2020 Methodology (.zip)

What is the difference between a country/territory’s rank and its score?

A country’s score is the perceived level of public sector corruption on a scale of 0-100, where 0 means highly corrupt and 100 means very clean.

A country's rank is its position relative to the other countries in the index. Ranks can change merely if the number of countries included in the index changes.

The rank is therefore not as important as the score in terms of indicating the level of corruption in that country.

What does it mean if my country’s score has gone up or down?

Small fluctuations or changes in a country’s CPI score are not usually significant, which is why every year in the full table of results [.zip], we mark all those countries that have undergone a “statistically significant” change. This is a change which is reflected in a majority of the CPI’s underlying data sources. When only a few data sources register a change, this means that it is not yet clear whether public sector corruption has gone up or down in that country.

Why is my country not on the list?

For a country or territory to be ranked in the Index, it must be featured in at least 3 of the CPI’s 13 data sources. A country’s absence from the list does not mean that country is corruption-free, only that there is not enough data available to accurately measure levels of corruption.

Approximately 180 countries and territories are included in the index each year.

Where can I find out more about corruption in my country?

The CPI is a very useful global indicator, but it is limited to experts' and businesspeople's perceptions of corruption in the public sector.

We produce complementary types of research on corruption, both at the global level and through our network of national chapters based in over 100 countries around the world.

For example, if you are interested in reading about how the people of a country experience corruption, our work through the Global Corruption Barometer would be ideal. It is the only worldwide public opinion survey on corruption.

If you would like to go beyond national borders to see how countries are doing in the fight against foreign bribery, explore our biennial report: Exporting Corruption.

We also answer very specific questions about corruption through our Anti-Corruption Knowledge Hub and HelpDesk answers.

The best way to find out what is happening with corruption in your country is to check out the dedicated country page.

What kind of corruption does the CPI measure?

The data sources used to compile the CPI specifically cover the following manifestations of public sector corruption:

  • Bribery
  • Diversion of public funds
  • Officials using their public office for private gain without facing consequences
  • Ability of governments to contain corruption in the public sector
  • Excessive red tape in the public sector which may increase opportunities for corruption
  • Nepotistic appointments in the civil service
  • Laws ensuring that public officials must disclose their finances and potential conflicts of interest
  • Legal protection for people who report cases of bribery and corruption
  • State capture by narrow vested interests
  • Access to information on public affairs/government activities

The CPI does not cover:

There was a lot of corrupt activity reported recently in my country, but I see that my country’s CPI score has increased. How could this have happened?

There are a number of possible reasons for this. Corrupt activity not within the timeframe of this year’s CPI could take a year or more to reflect in the data sources.

Some positive developments in controlling public sector corruption might have been captured, balancing out these negative cases. Certain types of corruption, such as money-laundering or foreign bribery, are not measured in the CPI.

The best way to find out what is happening in your country’s case is to check out the dedicated country page.

Why is the CPI based on perceptions?

Corruption usually entails illegal and deliberately hidden activities, which only come to light through scandals or prosecutions. This makes it very difficult to measure.

The sources and surveys which make up the CPI are based on carefully designed and calibrated questionnaires, answered by experts and businesspeople.

For more details about the data sources, the type of respondents and the specific questions asked, download the full information pack.

CPI 2021 Methodology

Can a country’s score in the latest CPI be compared with last year?

Yes. As part of the update to the methodology used to calculate the CPI in 2012, we established the new scale of 0-100. Each country score given by the underlying data sources is rescaled using the global mean and standard deviation from the CPI 2012 as the year of reference. Using this scale, we can compare CPI scores from one year to the next since 2012. Because of the update in the methodology, however, only CPI results from 2012 onwards can be compared.

I want to use the CPI results in my own publication – do I need to ask permission?

No. The Corruption Perceptions Index is covered by a Creative Commons Attribution-NoDerivs 4.0 licence, which means you are free to use our work as long as you credit and link back to us as follows:

CONTENT TITLE (YEAR) by Transparency International is licensed under CC-BYND 4.0

Please note that it is not permitted to remix or change any CPI content when re-using it.

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