As mine, and many others, CPC prices have declined dramatically YTD, it got me thinking/wondering how prices are really calculated. One of my sites is in a very high CPC industry on the Adwords side. However, the keywords bring the majority of the traffic to my site are long tail so there is not as many advertisers bidding on these keywords so it makes sense that my CPC for text ads is low. But I'm curious how Google calculates the CPC for clicks where the source of traffic was direct to site or perhaps the users came to the site via email marketing. How does Google figure out the CPC calculation when there isn't a keyword driving the visit? Hopefully I am making myself clear. I shouldn't be this ignorant given that I've managed sites for as long as I have, but I guess I really am pretty unaware how Google really calculates the CPC for text ads clicks.