I can't disclose which metrics are measured, sorry. Basically, they had to be at least metrics-neutral with strategic value (where "strategic value" means "some exec thinks this is a good idea and we really need to do it"), or pretty strongly metrics-positive without an exec's personal interest. Conflicts between CTRs on organic results vs. ads happen less often than you think, they're usually an issue only on full-page redesigns. I was an informed bystander for a few of them - I can't detail the precise process, but let's say that it's a complex balancing act that tries to balance the interests of all constituencies: users, webmasters, advertisers, and shareholders. (The one constituency that doesn't get a break are the poor engineers and PMs that have to implement it all..we often had some incredibly complex solutions to make the page marginally more user-friendly.)