28. November 2017

Sum & total number of visitors and visits. Why do the values not always match?

Tips & Tricks

1 Minute Reading time

by Katrin Nebermann

Irritating at first glance, but nevertheless correct: the Reports on the total number of visitors and visits are not correct always corresponds to the sum of the individual values. Why is that?

A simple example helps to understand these so-called “unique” or clear key figures: Assuming a website consists of from two sides. Two visitors come on one day. Visitor A only comes once and take a look at page #1 and page #2. Visitor B comes by once in the morning and once in the evening, looks at the only page #1 is displayed. Then the result for the on both sides that day:

	Visits	Visitors	Page impressions (PIs)
Page #1	3 (1 visit from visitor A, 2 Visits from visitor B)	2 (visitor A and visitor B)	3 (1x during the visit of visitor A, 1x visit in the morning from visitor B, 1x per visit in the evening from visitor B)
Page #2	1 (1visit from visitor A)	1 (Visitor A)	1 (1x during the visit of visitor A)

So far so good. Now comes the more difficult part of the total number:

	Visits	Visitors	Page impressions (PIs)
Summed total	4	3	4
Total (Unique)	3 (1x visitor A, 1x visit in the morning from visitor B, 1x visit in the evening from visitor B)	2 (visitor A and visitor B)	4

The pure addition therefore only matches the unique total number of page views.