In post last week, I emphasized what lots of others have already tried (without much apparent success) to point out: Prior to 2012, Transparency International’s Corruption Perception Index (CPI) scores are not comparable over time. The fact that a country’s score from one year to the next goes up or down might reflect an actual change in perceived corruption, but might be due to a whole host of other factors (changing aggregation methodology, changing scope of country coverage, change in perceived corruption of other countries, etc.), such that simple year-to-year comparisons are unreliable. In making this point, I was not criticizing TI itself, which has been quite clear that the pre-2012 CPI scores cannot be compared across years.
But what about 2012 and after? In 2012, TI announced, with much fanfare, that starting with the 2012 CPI and henceforth, scores across years would be comparable, due to changes in methodology (described here).
Is this right? If it were, it would be a huge benefit both to scholars and policy reformers who want to evaluate changes over time–and the impact of various interventions. Alas, after reading through TI’s discussion of the revised methodology, I regret to say the answer is probably no.