Sorting redaction by what the agency concluded shows the record is most opaque exactly where it is least explained. Cases left unresolved carry far heavier redaction than cases the agency explained; the handful flagged simply “redacted” are the most blacked-out of all.

Mean FOIA-marker density per page, by resolution status. Read it as a property of classification policy, not of the sightings: the most-withheld material is concentrated on the cases that were never closed. Confound — “unknown” cases are often thin scans where little is present to redact, so their low density is partly an artifact.