Since Google Analytics 4 is still under development, this is just an introductory article.
Google Analytics was plagued with custom reporting problems by mixing metrics and dimensions with different scopes (e.g. sessions for pages). Well, even though Google Analytics 4 is very different, it shares the same problem: it has dimensions and metrics that are user-scoped, session-scoped, event(hit)-scoped, and item-scoped.
These problems only appear when you start building custom reports, and the Data API (and the updated Google Analytics Pro connector from Analytics Edge) has enabled that. As with Google Analytics, if you stick to the combination of fields used in the standard reports, you will be fine. But when you start adding others to the mix, well, things start to get interesting…
As you can see, if you want to see what the difference is between the “Source” and the “Last click session campaign source” fields, you may find that Sessions are reported on one row with a Source value, but Views (a.k.a. Pageviews) are associated with (not set) values so they appear on a separate row (for the same page). It’s all a matter of scope and field compatibility.
If you used the Source in your report with a filter for ‘google’, you would under-report the Views. We need to learn the new valid metric and dimension combinations. In the meantime, be careful as you explore your data.
This is just a teaser…there are more mysteries lurking in those new waters of Google Analytics 4. We’ll figure our way through them soon enough…