The 2014 CPI Data Demonstrates Why, Even Post-2012, CPI Scores Cannot Be Compared Over Time

A little while back, I expressed some skepticism about whether Transparency International’s Corruption Perceptions Index (CPI) scores can be compared across time, even after TI changed its methodology in 2012 and claimed that its new scores would now be comparable across years.  More recently, I criticized TI’s 2014 CPI for burying the information on the margins of error associated with the CPI values, and for wrongly asserting that changes in the CPI score between 2013 and 2014 for certain countries (most notably China) were substantively meaningful.  (In fact, not only does the change in China’s score between 2013 and 2014 seem not to be statistically significant, but the change was due almost entirely to the dropping of a source in which China did abnormally well in 2013, and an abnormally large movement in a single other source.) I decided to follow up on this by taking a closer look at the other ten countries that TI singled out as having experienced significant CPI changes (in either direction) between 2013 and 2014.

Upon closer examination, I’m even more certain that CPI scores cannot be compared over time. I’m also more confident in my judgment that TI has been unforgivably sloppy — and downright misleading — in how it, and its representatives, have portrayed the substantive significance of these CPI changes. It turns out that the problem I found with the China calculations was not unusual. For almost all of the eleven countries TI identified as big movers, the CPI changes were driven by (1) the addition or elimination of sources from year to year for particular countries, and/or (2) abnormally large (indeed, implausibly large) movements in a single source. Until TI fixes its methodology, the safest thing to do is to ignore year-to-year changes in the CPI. And for the sake of preserving its own integrity and credibility, TI should either (A) persuasively explain why I am wrong in my analysis of the data (in which case I will gladly concede error), or (B) issue some sort of retraction or correction to its earlier press releases, and either drop the claim that post-2012 CPI scores can be compared across time or fix its methodology going forward.

Allow me to elaborate my analysis of the data: Continue reading