This all depends on how your system is set up and what your current design looks like. How do you know when an asset is active? Is it moving to a different status?
You might be able to use the Management Information Component. If you do have a status called "Active" then you could set up a query to only see assets in the active status. The Management Information Component will then run this query on a regular basis and from this create a report that will show you how many assets are on the active state throughout the year.
For more information on Management Information, see here
sorry i'm late
i think that the problem came over versionning of this field "Active"
without versionning it's impossible to have this information
i go to modify that
thank for your answer