Does anyone have statistics on the impact of robocallers? They're ubiquitous and universally obnoxious. I haven't seen any reporting on their effectiveness for

Does anyone have statistics on the impact of robocallers? They're ubiquitous and universally obnoxious. I haven't seen any reporting on their effectiveness for the services they're advertising for. I wonder why do they even bother. I understand these calls mostly take advantage of unsuspecting people, but I still can't imagine the impact these calls are making financially.