Mary Ellen, *,
If you have not come across it yet, Esri Labs has published the Activity Dashboard a free Esri Marketplace app that can be added to an Organizational account and allows more granular usage tracking including per user (30 day, 3 mo, 6 mo) details.
Link in the Esri Marketplace is here: https://marketplace.arcgis.com/listing.html?id=643bc71aec734874ba85866b0e444a4b
And once authorized/added, it is accessible from here: http://activitydashboard.arcgis.com, where after login there is an Open button linking the Organizational data. Including the "by User" stats.
Or if already logged into the Organizational account, this URL Activity Dashboard for ArcGIS
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