Andrea Moro's blog

Google Analytics sessions and your reports

About a month ago, Google Analytics introduced a change to the session visit calculation method. This will certainly have had an impact (and it will continue to have) on web sites traffic.

Before this change, sessions were counted only if one of the following circumstances were met:

  • Spend more than 30 minutes from the last page viewed (or spend the time you have specified in the function _setSessionCookieTimeout)
  • Strikes of midnight (midnight arrives for the time zone settings in the profile for that report)
  • Users close the browser, so they delete the session cookie __utmc

If any of three circumstances aforementioned were met, the next visitor pageview was considered a new session (visit). However, as of 11th of August, the last criteria has changed to “when the source of traffic change”. Therefore, the new calculation will still end the session in the first two cases as it was used to be, but it now not consider anymore a new visit when the user simply closes the browser.

A couple of examples to better understand the impact of the change made:

  • A user reaches your web site with a third party link, move away to a different site and find again a link to your site and enter.Prior the change, your user would have generated one visit only, from now on as the source has changed the sessions are two.
  • A user reaches your site throughout a search engine query, and then it performs another query with different keywords.
    Prior the change, your user would have accounted for one session only and the second keyword wouldn’t have had visits recorded. Now your site has two new sessions.
  • A user reaches your site via a PPC ad, leave the site and enter into the site using a different banner belonging to a different campaign.For Analytics we will now have two sessions.
  • A user reaches your site in one of the methods above, then close the browser, open it again within 30 minutes (or meanwhile your session timeout value) and reach your site directly typing the URL in the address bar.Analytics will now account for one session only. Prior the change these were used to be two visits.

As most of the changes introduced in the Analytics package, to me the rolling out time doesn’t seem the best choice Google made.
In fact, data prior to August 11 has not been affected by the change. This means a month with two measures, that to be honest with you could generate some sort of confusion amid the users.

Google stated that this change shouldn’t have impacted for more than 1%, but commentaries on their blogs and forums reported peaks of 45%, which is a massive (unpredicted?) spike.

Yes, that’s true, Google made this change to support their new multi-channel attribution funnels, but wouldn’t have been better roll out the change at begin of September? New month, new life?

What are the benefits?

According to Google, with new sessions being started for new traffic source information there will be a more accurate attribution.

With sessions not being automatically ended with the close of the browser for a short time, sessions can now model the user’s engagement with the website. However, it must be remembered that this change has impacted only the visit information (session), as conversions or e-commerce transactions were already being attributed to the new traffic source information.

I recommend you to stick a note in GA timeline as a reminder, in order to make it easier to debug any strange reporting issue.

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