Historical license/seat usage

I am slightly over-deployed and am creating a quote to add additional SEP licenses to our server.  Management would like to see what our actual usage has been (seats used) going back a year or two.  I checked the Reports tab and can't find a report showing historical usage.

Is there any way to determine how many licenses were in use by devices in the past (every month, quarter, year, etc.)?

Thank you!

Michael R.