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.