Suppose i have a keyword in an ad group and i delete that keyword from there and place it in another campaign or different ad group, would adwords reset historical data for that keyword in my account or will it somehow retain it.
I don't know the answer to this, but you could try a test using a keyword that isn't that important or do a test keyword.
Google maintains keywords history not only for you (as an individual) but across its entirebase. The only liberty u get that google has various parameters (geographical, website, keyword history in google regular search, kei analysis and lots of others) and because of several parameters, it sometimes gives u little time to test it. In this time, if google does not make money (or enough money) from you, then it is going to use its powers to disable that keyword(s). Sam - Economical Adwords Professional
Or they're going to try to hit you up for more money by making your keywords inactive hoping you increase your bids. Some of my inactive keywords are now turning active on their own. Also the activate bid amount they want on other keywords have dropped too. I realize they do this to hit you up for more money then when you don't "bite" they re-activate some keywords or lower the active bid amounts. I'm just assuming this is right from my recent limited experiences I'm not sure if this is 100% correct and what not.