The recent change in how Google Analytics tracks visitor sessions (see http://analytics.blogspot.com/2011/08/update-to-sessions-in-google-analytics.html) has had the following affect on the numbers you see within Google Analytics:
The change to Google Analytics was related to how visitor sessions are seen as finished and a new session started. The change was meant to affect visitors arriving from one traffic source and then coming back on another, for example clicking organic and then clicking a PPC ad within 30 minutes used to be one session, it is now two sessions.
- Visitor numbers – these skyrocketed after the update but have returned to more normal when they fixed the bug on 8/17/2011 (see linked post above). The numbers now are slightly higher than they were previously due to changes in the way sessions are counted.
- Pages Viewed – this number is not affected by the number of visitor sessions and appears to have not been affected by the recent changes.
- Pages per visit – this number will be lower now due to visitor numbers going up but pages viewed not changing.
- Bounce rate – this would have gone up as now a single session can be seen as two sessions which can mean that a visitor clicking through from organic, then clicking a paid ad would be seen as one bounce and one return visitor.
- % new visitors – this would have gone down due to what was previously one new visitor session now being one new visitor session and one repeat visitor session.
- Average time on site – this would have lowered as where there was one session previously is now seen as two sessions.