Such ratings are not reliable. Read this:
But conventional corruption perception measures (including those use to construct the CPI) have well-known problems, including limited coverage (with respect to both years and countries) and relatively low frequency (usually annual). And they rely on the perceptions of a handful of experts, which may not necessarily be representative. These limitations mean that while traditional perception measures like the CPI may be useful for some purposes, they are not as helpful for others, such as measuring the impact of individual events or news reports on corruption perceptions, or how changes in corruption perceptions affect government approval ratings.
Posts about Google Trends written by Matthew Stephenson and Christoph Nedopil
globalanticorruptionblog.com
Also this from 2018 by a law professor at Harvard who runs the global anti corruption blog:
Moreover, the title of TI’s press release, “Corruption Perceptions Index 2018 Shows Anti-Corruption Efforts Stalled in Most Countries,” is just wrong, and in a way that matters:
First, because there’s so much statistical noise, the fact that most countries haven’t exhibited a statistically significant improvement doesn’t mean things haven’t improved. That’s just an inherent problem with noisy data: small movements might not mean anything, because it might just be noise, but at the same time the noise in the data may prevent us from detecting genuine improvements.
Second, and perhaps more important, anticorruption efforts take time to be effective, and it would be a mistake to write them off as a failure just because they don’t produce an immediate, detectable improvement in a country’s CPI score. I know TI means well here–they want to emphasize the seriousness of the problem and the urgency of devoting more energy and resources to combating corruption. But as we’ve noted on this blog previously (see, for example, here and here), interpreting a lack of change in the CPI as evidence that anticorruption efforts aren’t working can be counterproductive: They can be demoralizing, and breed more cynicism and fatalism, attitudes which themselves make corruption harder to control. Now, if the CPI data really did show conclusively that anticorruption efforts aren’t working, then the fact that spreading that message might have demoralizing effects might not be a good argument for suppressing or downplaying this truth. But since a lack of statistically significant changes in the CPI data does not clearly show that anticorruption efforts have “stalled,” putting this spin on the data is a rhetorical choice, and I fear a misguided one.
Today, Transparency International released its new Corruption Perceptions Index (CPI) for 2018. At some point, hopefully soon, I’ll have time to look closely at the new data and accompanying …
globalanticorruptionblog.com