The number of users reported in Yammer does not seem to match the user statistics in SWOOP. Why not?
In SWOOP, if a person had a Yammer account at any time during the selected time period, then that person is included as a user.The report that can be downloaded from Yammer also includes a state (one of these is 'active') for every user which is correct as of the date you download the report. Therefore there can be a difference in the numbers.
If 'Yesterday' is selected from the settings wheel in SWOOP (Enterprise tab), that will return a total number of users on that specific day which will be the closest to the number reported by Yammer.