A new report compiled by the Columbia Law School Human Rights Clinic and the Sanaa Center for Strategic Studies has found that the United States only admits officially to about one fifth of their drone strikes which end up killing someone, saying this hurts accountability.

That the US has been deliberately evasive about its drone program is hardly news, but this appears to be the first study aimed at specifically figuring exactly how many lethal drone strikes have been officially acknowledged.

This has been a growing problem with US airstrikes in Iraq and Syria as well, with official Pentagon figures on civilian death tolls dramatically lower than those recorded by private NGOs, with the difference often a factor of ten or more as the US downplays the tolls.

In the case of the drone strikes, it’s less about covering up civilian deaths than all deaths and the scope of the drone war, because little to no effort was ever made to identify who was killed in specific drone strikes, and the only times names were made public were in the very unusual cases that someone was killed who had previously been heard of by the military.

Drone strikes were limited through the end of President Bush’s second term, and grew rapidly under President Obama. While the rate of drone strikes dropped near the end of Obama’s time in office, they appear to once again have begun growing substantially under President Trump’s watch, bringing back concerns about how the US has long mishandled reporting on the operations.

The Columbia report was particularly concerned with the lack of transparency in “lethal” operations, irrespective of who they actually end up killing, noting that it’s impossible to ensure proper accountability, particularly when those lethal actions end up killing innocent bystanders, when the government won’t even keep formal track of how many killings they’re taking part in.