In the Optimization experiments, there's a Quality Score as well as a revenue score.

I'm currently running an optimization experiment on adding a visible border to my ads. Revenue is significantly down (25% down) but the Quality Score is up by over 175%. It's currently indicating an Overall Change of over 150%.

There's scant information anywhere about the AdSense Quality Score. There's a small piece of information on the Google AdSense Support pages, at [support.google.com...] which says, in part:

In general, a positive Overall Change will result in better long-term performance, even when either the RPM change or the Quality Score change is negative.

There doesn't appear to be any discussion about Quality Score as it applies to AdSense here, and very little discussion on the web in total. I wondered whether members here had any advice or experience: it would appear that the Quality Score is the secret for longer-term performance, even though I can ill afford a 25% drop in earnings.