QUOTE: “The average duration metric for the particular group of resources can be a statistical measure computed from a data set of measurements of a length of time that elapses between a time that a given user clicks on a search result included in a search results web page that identifies a resource in the particular group of resources and a time that the given user navigates back to the search results web page. …Thus, the user experience can be improved because search results higher in the presentation order will better match the user’s informational needs.” High Quality Search Results based on Repeat Clicks and Visit Duration
Over the past few days or so, I have been seeing chatter both at WebmasterWorld and Black Hat World around ranking and traffic changes related to Google organic search. I got to say, I doubt Google pushed anything specific this week or even next week. Rankings do change by itself and new content is always being added to the index but an algorithm update - I doubt it.