General Discussion

On Wikipedia, the CPI has a criticisms section highlight many of its flaws. You could read up on that if you want. There are plenty of articles on this too.

The TLDR seems to be: not politically motivated, the CPI isn't blatant propaganda. However, it does not cover all forms of corruption, it has a bias towards "perceived" corruption, and it is strongly biased against lower income nations.

As with many of these kinds of indexes, they are a decent-ish generalisation of the issue but are not enough to accurately depect such a complex topic.

A bit more reading has found that many people criticise CPI as it cannot fully represent all kinds of corruption, especially those in lower income areas.

There are people on both sides, arguing that places like China should be lower on the index, since "perceived" corruption could be influenced by China's strict control of the media. Others note that the index does not account for cultural differences and is biased towards perceived corruption over actual improvements, and that China should have a better score due to their efforts in cracking down corruption. But both sides agree that a simple index cannot cover the complex nature of corruption, which has many layers to it.

I don't think the index itself is politically motivated, at least not in the sense of being complete propaganda fabricated by the Americans. They do highlight the improvements and declines in the transparency of institutions and strength of justice systems around the world.

However, a single number cannot cover the wide topic of corruption, and there is no distinction between the different forms of corruption.

One more thing, I found an article by "the British academy" written by Professor Pail Heywood from the University of Nottingham relating to this topic. They say that Transparency International is helping to increase media attention and public awareness of corruption, and has helped to push many nations to adopt anti-corruption legislation.

However, he highlights that it is flawed in that it's biased towards perception of corruption. noting that they focus too much on bribery (since many of the CPI's sources are from business executives and the like), and that one number can't accurate represent corruption in an entire territory, and that corruption can vary oj a local level.

Professor Heywood's main point of criticism though is how it puts some nations into a poverty trap, where aid is restricted for lower income countries, as they lack the strong democratic institutions that are deemed by the CPI as necessary to combat corruption, yet those are the nations where liberal democracy is incredibly difficult to establish.

I am unsure of this professor's reputation, but he seems to know what he's talking about at least. I'm not any sort of political scientist or international relations expert, so take it for what you will.

Yes, I was looking into indexes like that, it's just funny to me that in many western countries in billions of dollars disappear in one "dirty lil deal", the witnesses get silenced, the evidence disappears, the investigations stop, while many of those "red ones" probably total that amount in a year ;)