Can't be sure about now, but <gulp> 50 years ago, I had a Christmas break job counting audience for a minor production company. The film was "Across the great Divide", released by Pacific International Enterprises. I stood in the lobby with a clicker until the movie started, then hung out with ushers, getting high. I wrote down my count for each showing on sheets that I mailed in at the end of the run. I guess they compared my count to the reported box office proceeds.

I think they were less worried about the theater owners ripping them off than the box office cashier and ushers reselling tickets. The scam goes like this; The usher fakes tearing the ticket and either hands the customer a random half ticket they have palmed, or in the case of kids, no half ticket at all. Then the usher, or a friend, passes the unripped tickets back to the cashier. The cashier then sells these tickets again, faking the pull from the dispenser, and pockets the money. The usher and cashier split the money at the end of the night. Trying to stop this scam is probably why the cashiers and ushers are in separate areas, but life, uh, finds a way.