How Does the New Google Analytics Visits Algorithm Affect Your Data?
Sep 23, 2011 by John Curtis
Google Analytics recently changed the way visits (or sessions) are counted. Previously, if you were to visit a site, leave the site, and return via a different source - GA counted that as a single visit but gave credit to each source (subsequent sources counting for pageviews, but as 0 visits). Only the first referral source counted as one visit. The others had this weird zero visit attached to them. The zero visit nonsense is now history, as GA will now begin a new session with each new referring source. But how will that impact your data if you're comparing it to data before August 11 (when the change took effect)?
We've had some clients ask us about this, so I want to hand out a couple of resources on understanding the matter. First, it's very likely that the data skewing will be small. This custom GA report from Michael Whitaker allows you to determine what percentage of visits to your site were "zero visits" prior to the change. It's probably under one percent. Here is a screenshot from a fairly high-traffic dealership we work with showing that only 0.93% of visits in the month prior to the change resulted in zero visits.
What is affected?
Your data will be impacted slightly. As Avinash Kaushik points out in his great video on this subject, you can always trust your Pageviews and your Unique Visitor data. That can't change. What will change with this new algorithm for tracking visits is your Avg. Pages/Visit, % New Visits, and Bouce Rate most notably. But again, this hinges on how much of your traffic before the switch was part of that zero visit group. If it was under one percent of your total visits, you won't notice drastic changes in these metrics.
Why did Google Analytics do this?
Because it's better. It makes so much more sense to attribute visits by each individual referring source. And with what Google Analytics has now done with Multi-Channel Funnels, it makes even more sense for better attribution.