I'm migrating a high-traffic site from Classic Analytics (ga.js) to Universal Analytics (analytics.js). Both setups have been running in parallel for the past few days: ga.js is hard-coded on the pages (i.e. "_gaq" calls) and analytics.js is running through Google Tag Manager (GTM) with the standard integration for pageviews. Furthermore, both GA properties and views are configured exactly the same, and there are no interactive events (or similar) that could be causing big discrepancies.
There are some really strange discrepancies in the data, which I can't fully explain. For example, looking at yesterday's numbers, analytics.js reports:
- 4% more sessions (~5,000)
- 1.5% more users (~1,500)
- 2% less pageviews (~7,500), and mostly flat unique pageviews
- 6% less pages/session (2.69 vs 2.85)
- 10% lower avg. session duration (00:02:31 vs 00:02:48)
- 2% higher bounce rate (50.4% vs 49.4%)
I started drilling down into the reports and, so far, the biggest differences I can find in the analytics.js property are:
- 15% more Direct sessions (~3,200)
- 115% more sessions from "UC Browser" browser (~3,500)
- 130% more sessions from "level 3 communications inc" ISP (~2,100)
- 320% more sessions from the city of Putney (~1,700), with the majority of the increase attributed to "UC Browser"
- 200% more sessions from Dubai and Beijing.
While I know analytics.js is supposed to be better, I'm having a very hard time explaining such large discrepancies, especially when it comes to the higher sessions, lower pageviews and time on site: these are moving in contradictory directions.
I would really appreciate any ideas on the following:
- How is it possible that I'm seeing so many more sessions, but less pageviews?
- Why is avg. session duration drastically different?
- Are there any other factors that could be causing such discrepancies? Especially the inflated session number.
- Should I move analytics.js entirely out of GTM?
Any other ideas are greatly appreciated.