Does anyone factor the value of ad impressions into their ROI for AdWords?
Being that CTR is a major driver of Quality Score which is a major driver of CPC which determines the cost which determines the ROI - then, yes. :)
Ignoring what happens before the click is ignoring a pretty major determinant of how much you're paying...
There is a dance between more total impressions and lower converting clicks vs fewer impressions and higher converting clicks.
Here's a thread that looks at how to split test at the impression level:
[webmasterworld.com...]
