Many of you know how the Google AdWords ranking process works. Google looks at your bid and click through rate and multiplies them to get a "rank number". They use the rank number to determine the location of the ad in relation to other ads on that network for that keyword phase.
At WebmasterWorld, a member asked How often is CTR re-evaluated for bidding purposes?. Based on my understanding of AdWordsAdvisor's response, it seems as if this is a continuous and almost real time number. Someone then goes on to ask, if Google just looks at the CTR of the last 1,000 impressions. AdWordsAdvisor responds that they do not, they do weigh the last 1,000 impressions higher then the past impressions, but they look at "all-time CTR for the keyword."