The survey found that 67% of all searches in August were done using Google, but only 65% of those prompted a user to click on a result. Yahoo, on the other hand, accounted for 20% of all searches in August, 75% of which resulted in a referral.
Compete makes an interesting argument on search effectiveness – not a flawless one, though. In reality search effectiveness is much more complicated than that. Matt Cutts, head of Google's Webspam team, noted on Compete's blog that sometimes searchers get answers from the snippets that appear on Google’s results page, doing away with the need for users to click on a link, while on Yahoo "you don't get any OneBox answer, and the snippets are unclear," he said. I, for one, prefer Google, but regardless of which engine is more effective, it is interesting to look at it from different perspective.