I should also clarify that my figures are slight underestimates of the actual figures: I can only "see" Mechanical Turk through the eyes of an average worker. S

I should also clarify that my figures are slight underestimates of the actual figures: I can only "see" Mechanical Turk through the eyes of an average worker. So I cannot see if a requester asks multiple people to complete the same HIT and, sometimes, I cannot observe the details for HITs for which I have not passed the qualification test. I still think that the numbers will be at the same order of magnitude. I am not sure if that's a valid assumption. Almost every HIT I've written has been at least 2x (and typically 3+x) for redundancy. It is cheaper/faster to code for consensus than verify results. I have seen several HITs for which the task is likely massively redundant.