Google decided to sunset Classic Analytics, and all sites were required to upgrade to Universal Analytics. If site owners didn’t upgrade manually, Google would automatically upgrade the sites. Universal and Classic Analytics differ in how they track site sessions by default. While both versions of Google Analytics defaulted the session timeout to 30 minutes, Classic Analytics did not trigger a new session when the session arrived from a referral. Since sessions are automatically timed to be 30 minutes , site visitors who start navigating your site but become inactive and then resume more than 30 minutes later are starting a second session. In Classic Analytics, if the visitor arrived by a certain channel and that session timed out, the visitor’s new session when he/she resumed activity would remain as the original channel
How this becomes a problem to organic measurement?
The effectiveness of our SEO efforts depend on the source/medium. If site traffic isn’t being attributed to the correct source/medium, then we are not working with accurate data sets.
Read more: http://searchengineland.com/google-anal ... lue-257636