Why you should be careful when you see new and returning visitors in Google Analytics

Google Analytics can sometimes be mean, because some dimensions paired with segments do not behave as you might think at first. Thanks to Michael Janssens and Maik Bruns’ comments on my question in the analysis group founded by Maik, I can go to sleep today with peace of mind and have become a little smarter again.
The question came up today in the Analytics course: How can it be that I have more new users than transactions when I am in the “Has made a purchase” segment? The link to the report is here, the assumption I had was that: If I have a segment of users who have made a purchase and use that segment in the “New vs. Recurring Users” report, I assume that in the New Visitors + Have Made a Purchase section I see only those users who made a purchase in their first visit. However, here in this report we see 691 users, but only 376 transactions. If my expectations were right, then the number here would be the same. But it is not.

New users + Recurring users > All users

We also see other contradictions here, and for the sake of completeness we begin with them. The number of new users is 53,263, the number of returning users 14,578. However, we have only 58,856 users in total, less than the sum of new and returning users.

This discrepancy is simply explained: if a user comes for the first time within the reporting period, then he is a new user. If he comes a second time within the reporting period, he is also a returning user. He is therefore counted twice, once for new users and once for returning users. With “All users”, however, he is counted only once.
If we take a look at the Transactions column, we see that these are not counted more than once. This is logical, because you can only define yourself as a transaction once ­čÖé

Global pages distort the data

Maik added the point that global pages have some distorted data because Google Analytics restarts all sessions at midnight, so a new visitor who arrives at 23:55 and calls up a second page at 0:01 on that second day is also considered a new visitor, just like on the first day. It is the same user, but he is counted twice as a new user (see source here). But can this mean that we have so many more new users than transactions? Of course, the Google Merchandising Store is globally galactically active, but is so much bought around the clock?

The solution: No Boolean AND

The solution (thanks, Michael!) is that the segment “Made a Purchase” paired with “New Visitor” is not linked with an AND, i.e. we can have users in it who have bought sometime, but not necessarily in the first visit. This becomes clear when we compare our two segments with a segment that Michael built:

Michael’s segment is built to use the AND link:

We have sessions here where a user has to be new and at least one transaction at the same time. And we suddenly see that we have 373 users for the 376 transactions, i.e. there must have been users who had several transactions during their visit. In other words, the New Visitors in our “Made a Purchase” segment all made a purchase, but 691 minus 376 transactions were not made by these New Visitors during their first visit, but in a later one. The link between the report and the segment could be formulated in this way: Show me all users who had a transaction in any session and their first visit within the reporting period. It doesn’t mean show me all users who also have a transaction in their first session.

In the future, I will take a closer look at how to interpret the link between a segment and a report. Because that was, as I said, something mean ­čÖé

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