Jack Thurston of Farmsubsidy gives here very good insights on the problems in data availability and illustrates one example of measuring transparency.
Some important variables are described: format of data, completeness of data, timeliness of data.
Which of course reminds me of the 8 principle for reuse of public data.
I will have a look at the methodology, maybe this could be re-used for other kind of public data?

Farmsubsidy.org Newsletter: Issue 1 | farmsubsidy.org