We recently changed our site and blog design. For our blog we received this message in WMT: Big traffic change for top URL: Search result clicks for this URL .... have decreased significantly.
The message goes on to recommend action, one of which: Some content is popular only for a short window of time. If the change in traffic affects only this kind of content this message may not be indicative of any problem
My question is how does Google know what is popular and not popular? It also seems like popularity of a page is seldom mentioned as a Algo signal, but from this message, it seems like a big factor.