Anecdotally, I've noticed a decrease since a few months ago (my call blocker log shows 1 call in all of January) and I've been picking up, striking up a conversation for 10-15 seconds then continuing the same with hardcore insults in a relaxed, deadpan manner, as if we were still discussing their IT assistance/credit card "refund"/cruise/security system offer. If they start yelling I just hang up. Some people try to keep selling me their crap, that is funny; I've got quite a few stunned silences punctuated by huffs and puffs, and I made one scammer sob, that was great (I guess whatever I told him about his call center job was accidentally well targeted); so it's also great entertainment and takes very little time, you can have them on speakerphone and keep working/reading/working out/etc.