Also, to clarify something else... ad CTR is usually based more on the advertiser themselves than anyone else. If two advertisers create their ads, they will have different CTR's, even when on the same content. There have been ads that run a 0.00% CTR because they flat out suck, and others than convert 10%+. When you bring revenue into this as part of determining how much each writer's "value" is, you're not only basing it on THEIR work, but also the advertisers', something the writer has absolutely no control over.