Looking at the tech, well, okay going off my memory right now... I remember I had 11% corruption at one point, so I went and finished up Tier I of Philosphy I think, which says it'll reduce corruption by 5% in your provinces. So I was expecting a nice income boost when it finished... but I noticed, it hadn't gone up at all. Checking, the corruption was still listed as 11% in my provinces. Getting the actual tech that does -5%, also didn't seem to do anything.

By that point my corruption was at 16%, but again getting the tech didn't seem to do anything. Are they not working or something? Or do they work in some way I'm not understanding? Darn corruption, stealin' my Talents.