Robert_Charlton - 1:32 am on Jul 23, 2013 (gmt 0)
I don't think it's Analytics. We've had a lot of discussions about where Google might get the data... speculating about everything from ISP data to DoubleClick... and Google may correlate what they see elsewhere with Analytics averaged over a bunch of sites, but Analytics by itself wouldn't even provide Google with a consistent data set.
If searchers come back to Google, Google probably has recent google.com cookie data on the searcher... no matter what the browser. See this thread for some interesting thoughts...
Panda Metric : Google Usage of User Engagement Metrics
I think they're measuring things like engagement, stickiness, and not coming back to search again on Google... and lower price might correlate with all of these things.