I'm trying to find some history on previous round difficulties. Doesn't seem to be any. Some nice graphs here I suppose: http://bitcoin.sipa.be/
Seems like difficulty is projected to go up pretty steeply in the coming months. I'm trying to come up with an estimate for diminished rate of return on my mining setup.
EG., next round of difficulty will be around 1379048 which will drop mining productivity by around 30%. Might one assume a constant rate of decline like that or is it projected to be even more accelerated?
Curious what work / articles have been done on this subject.