Data layer events are inaccurate

Since I started using Piwik Pro, the number of custom events being tracked is not accurate anymore.
Before, with Universal Analytics, for example, the amount of sold subscriptions matched exactly the amount that I count in the backend of our website.

Notice that these are data layer event, so they should trigger exactly the same in Piwik Pro as they did in Universal Analytics.

I assume it has to do with the settings in Piwik Pro, I already:

  • turned of “Respect opt-out and DNT”
  • we exclude the same IP adresses as we did in Universal Analytics

Does anybody have any idea how this is possible?

How big is the difference? Can you share your current setup? Are you using any other tool to gather conversions? I’d start by checking if there were any broken events. You can check that in Administration → Settings → Subscription → Action details.

How big is the difference?
It really depends. For example, in August we saw 151 sold subscriptions in the backend of our site but Piwik Pro tracked only 139. For oktober it is only a difference of 2 sold subscriptions.

Any broken events?
I checked Administration → Settings → Subscription → Action details and there are no broken events.

Are you using any other tool to gather conversions?
At the moment there are also still conversion being tracked by Universal Analytics via Google Tag Manager.

Can you share your current setup?
See attachment.

Thank you very much in advance!

Thanks for sharing. I see that this tag requires Analytics consent. Is UA configured in a similar way? Being honest, tracking more than 90% of transactions is a good result given all the tracking prevention mechanisms and adblocks that we have on the market. It’s a statistically significant sample to perform analysis.

Thanks for your response. I agree that more than 90% accuracy is “good enough”.

However, I am a bit curious to find out where this exact difference comes from. I feel like I checked all possible reasons (settings regarding tracking, cookies,…)

Is there any chance it has to do with the fact that the Piwik PRO tracking code is installed via Google Tag Manager instead of hard coded in the site?

I don’t think so, since you’re using the very same container for Google Analytics.