Moreover, the CPI becomes even more important as the leading global indicator of cross-country perceptions of corruption in a time when corruption tops headlines and factors into aid allocation.

Launched on 6 November, major newspapers around the world have reported its findings, including the BBC, Financial Times and the International Herald Tribune. So what exactly is the CPI? Transparency Watch lists some of the most frequently asked questions below:

What is the Corruption Perceptions Index (CPI)?

Transparency International’s (TI) Corruption Perceptions Index (CPI) ranks countries in terms of the degree to which corruption is perceived to exist among public officials and politicians. It is a composite index, a poll of polls, drawing on corruption-related data from expert and business surveys. A country must have at least three sources to be included.

Whose perceptions does the CPI measure?

Surveys are carried out among business people and country analysts. The surveys used in the CPI use two types of samples, both residents of the country non-resident country experts.

Why is the CPI based only on perceptions?

It is difficult to assess the overall levels of corruption in different countries based on hard empirical data; for example, by comparing the amount of bribes or the number of prosecutions or court cases. Obtaining reliable data on the amount of bribes would be extremely difficult, and comparing data on prosecutions may tend to highlight the quality of prosecutors, courts and/or the media in exposing corruption across countries, rather than actual levels of corruption. One strong method of compiling cross-country data is therefore to draw on the experience and perceptions of those who are most directly confronted with the realities of corruption in a country.

Which matters more, a country’s rank or its score?

A country’s score is a much more important indication of the perceived level of corruption in a country than its rank. A country's rank can change simply because new countries enter the index or others drop out.

Is the country with the lowest score the world's most corrupt country?

No. The country with the lowest score is the one where corruption is perceived to be greatest among those included in the list. There are more than 200 sovereign nations in the world, and the latest CPI 2006 ranks 163 of them. The CPI provides no information about countries that are not included.

Is the CPI a reliable measure of a country's perceived level of corruption?

The CPI is a solid measurement tool of perception of corruption. As such, the CPI has been tested and used widely by both scholars and analysts. The reliability of the CPI differs, however, across countries. Countries with a high number of sources and small differences in the evaluations provided by the sources (indicated by a narrow confidence range) convey greater reliability in terms of their score and ranking; the converse is also the case.

Is the CPI a reliable measure for decisions on aid allocation?

Some governments have sought to use corruption scores to determine which countries receive aid, and which do not. TI does not encourage the CPI to be used in this way. Countries that are perceived as very corrupt can not be written off – it is particularly they who need help to emerge from the corruption-poverty spiral. If a country is believed to be corrupt, this should serve as a signal to donors that investment is needed in systemic approaches to fight corruption. And if donors intend to support major development projects in countries perceived to be corrupt, they should pay particular attention to ‘red flags’ and make sure appropriate control processes are set up.

For more, please see Transparency International’s In Focus on the Corruption Perceptions Index 2006 at: www.transparency.org/news_room/in_focus/cpi_2006