Assessed Assets past xx days

Trying to come up with a way to show why the number of assessed assets has dropped over the months. I have my thoughts, but the boss wants some proof. He is getting this info from the Assessed assets vs Risk Score card, but other than a line graph it provides no further information. Is there a SQL query to show this information?

You could take a look at the fact_asset_date table in the reporting data model to run a query over the last 13 months for example and tell it to spit out a weekly or monthly interval. It will essentially give a line for each asset within that interval by the ID so you could get a list of which asset ids belonged in last month that do not exist now.