In the US, a reasonable estimate is dozens of murders per year. I don't know if we can do any better without running a study: There's no good data easily available; the murder clearance rate in the US is now quite low; most insurance killings are, of course, staged to look like accidents.

But it's enough of a problem that there are quite a lot of legal journal articles about it, e.g.: https://scholarship.law.campbell.edu/cgi/viewcontent.cgi?art...

Life insurance has killed a lot of people. People who would otherwise be alive but for the existence of payouts upon their deaths.