Clearance rates for homicide have _dropped_ over the past 50 years:

  America’s homicide clearance rate—the percentage of solved
  crimes that lead to arrest—has fallen considerably in the
  past 50 years, from around 90% in 1965 to around 64% in
  2012, according to federal statistics.

(https://www.economist.com/news/united-states/21656725-police...) (See, also, https://www.citylab.com/equity/2017/06/police-arent-getting-...)

IMO, similar to counter-terrorism efforts (most spectacularly, 9/11), technology becomes a crutch. Frankly, I wouldn't be surprised if mass encryption leads to _improved_ clearance rates, as law enforcement becomes less complacent. Take this latest example: the FBI agent declines Apple's help because he's convinced the geeks at the FBI lab can handle it. He presumably doesn't bother actually confirming with the geeks in the lab, nor does he attempt to put Apple in touch with the lab. Just utter complacency, confident that the machine (computers, bureaucracy) will suffice.

This sort of laziness wouldn't have been tolerated in Hoover's FBI. Moreover, Hoover likely would have been more aggressive using the tools available to him--keyloggers, etc--rather than whining.

Given that we're now learning that many of the convictions won last century were based on bad evidence and corrupt behavior, I don't really put much stock into those figures.

Wouldn't that be a change in data collection more than in absolute quality of problem-solving? Japan, for example, I remember reading that their near-perfect homicide rate is actually because they'll classify it as "fell down some stairs" if they can't solve it. Particularly in the US with its history of social issues, I can easily see a ton of homicides in the 50s just never being written down.

I lost the link, but another newspaper article said that the clearance rate for homicides of whites dropped from, IIRC, 90% to 85%. So, yes, part of it is social issues. But in any event, it's an interesting fact that official clearance rates have moved in the opposite direction of advances in technology and ease of remote surveillance. Technology doesn't solve our social issues, and in fact can exacerbate them.

Regarding Japan, yes, their official rates are questionable. I wish I could find the journal article, but last year I was researching the supposed 100% clearance rate in Singapore and came across a very in-depth article[1] that discussed clearance rates in Singapore, Japan, and elsewhere in Asia and that left me with the impression that w'ever the actual clearance rates, they're nonetheless _much_ better than the U.S.

[1] Spoiler: the 100% clearance rate in Singapore was plausible, in no small part because it's a small city-state with very few homicides to begin with.

Or homicides that were attributed to some person that it was convenient to lock away and who were unable to prove their innocence.

A good example of this is sexual assault cases on campus. A lot of times they try to handle them without getting the real police involved, or attempt to downplay everything about it to keep the statistics pointed one way.