Transparency International, the only global non-profit group dedicated to rooting out corruption, is in a curious position. The Berlin-based organisation is best-known as being the creator of the Corruption Perception Index, a ranking of countries according to how corrupt they are perceived to be. It is a measure of Transparency's success at holding up the theory and practice of corruption before the eyes of the world that such a piece of arcana is quoted and referenced ad infinitum. It is indeed a defining index of our times, a mirror for all things corruptible and morally corrosive.

It is also an index that is contentious and fraught with argument. It evokes strong reaction from actors as diverse as peeved prime ministers of countries that rank low on the list, outraged statisticians for whom the intangible world of bribery is scarcely one that can be reliably mapped. It is nonetheless standard equipment for CEOs who steer multi-billion euro investment decisions from one country to another based on whether it lies a few places above or below an acceptable level on the all-seeing index. Like the search engine Google's well-known experiments with maintaining social snapshots of our online world based on the most used search terms, the index provides a zeitgeist of the shadowy world of graft and pelf.

That is the aura surrounding the Corruption Perception Index - its reach and power is enormous. The truth however takes the shine off the edifice. That the index and Transparency International (TI) have become synonymous to the exclusion of much of the other good work that the non-profit does and initiates is neither what the organisation wanted, nor the intent of the Corruption Perception Index (CPI). It is threatening to become the tail that wags the dog, and while the Transparency universe - more than 85 chapters in over 90 countries - is concerned about the brand impelling its maker, the effort to have the CPI measured against the rest of the non-profit's work has not been helped by the emergence, in December 2004, of yet another instant measure, the Global Corruption Barometer.

This when there is already a healthy and growing criticism of the intent and methods of the index. Most of the most constructive comment comes from those familiar with Transparency's mission and who also see the need for a more catholic view of the phenomenology of corruption, with the inescapable truth that indices are essentially incapable of quantifying the tremendously varying experiences of corruption.

The luxury of the studied approach is not however available to one constituency that is amongst the primary consumers of the index: the media. For a constituency that is used to digesting bullet-point presentations and top ten QuikLists of everything from diapers to rogue states, the CPI is made-to-order for that single column down the side of the front page. And it is precisely because of its careful attention to how it can be consumed and re-exported that the index in fact trips spectacularly over itself.