By far the most interesting indicator is the percentageof people who report paying a bribe in the past 12 months (more precisely, the percentage of households who paid a bribe when accessing basic services). It is as close to objective measurement as you can get in a sphere of life as indefinite and necessarily opaque as “corruption.”
You can take a look at a global interactive map here: https://www.transparency.org/news/feature/global_corruption_barometer_citizens_voices_from_around_the_world
Access to the global data here in Excel format: Global_Corruption_Barometer_2017_Global_Results
More regional maps (where available), with a few comments comparing results to the GCB 2013.
Europe – Romania, Hungary, and Lithuania are the most notably corrupt EU countries; Greece, in fairness, has improved substantilaly since the last assessment in 2013, when 22% of Greeks paid bribes.
Ukraine didn’t budge relative to 2013; was 37%, now 38%. Both the Ukraine and Russia are much worse than Belarus. This confirms stereotypes, BTW.
East Asia – India has actually deteriorated further, from 54% in 2013. Taiwan’s figure is much more plausible than the anomalous seeming 36% in the last survey.
Latin America – What is going on in Mexico? It was 33% last time.
It appears that North America will not be covered in this round of the GCB. For comparison with its southern neighbors and Europe, the reported bribery rate in the US was 7% in 2013 (up from 5% in the survey before that, and 2-3% in the oldest surveys).
The bribery rate in Canada in the last GCB was 3%.
Middle East – This is pretty interesting – Tunisia is basically a European Mediterannean countries in this respect (Greece: 10%; Italy: 7%).
Algeria not bad either at 14%. Perhaps explains why there hasn’t been an Arab/Islamist “spring” there against its ageing rulers.
Africa – This concisely explains why Botswanans manage to maintain a pretty nice state despite very low average IQs (they have natural resouce rents from diamonds, ofc, but so does Equatorial Guinea – and far more of them – but that doesn’t translate into normal living standards for its 99%).