Murder rates are also down substantially since the 1990s. The leading theories include reduced lead exposure and fewer neglected and unwanted children thanks to reproductive healthcare. In either case, the missing murderers would’ve been more impulsive, more careless, and easier to catch. Many of the murders that go unsolved today, likely would’ve gone unsolved in the past, too.

Plus, some of the cleared murders in the past were simply blamed on innocent black men by a racist system. Look at the Innocence Project for examples. We still have a problem with all that, but surely it’s not as bad as it was in the 1970s.

Another contributing factor is that so much forensics and police resources are wasted on victimless drug crimes. It’s an lot easier to bust a corner boy selling drugs than to track down a murderer.