I do not know of any formal study. As you would expect dealer errors tend to decrease as the quality of the casino goes up. I have personally played thousands of hours behind the tables since I turned 21 years old 19 years ago (it seems like just yesterday). Based on all that play I strongly feel that most errors favor the house, probably about 80%. For example many dealers do not know that you still pay the ante bonus in Three Card Poker even if the player lost or the dealer didn’t qualify. (Bluejay got shortchanged this way because he wasn’t sure of the rule himself.) I’ve had a few dealers disagree with me on this rule, who were later correctly overruled by the pit boss. I wonder how many players, who don’t know the rules as well as I do, were shortchanged by these same dealers before I played. Of course the error is more likely to be corrected if the error favors the dealer. I tend to think the cost of errors to the casino is not very high because of the higher percentage in favor of the dealer. In fact I wouldn’t be surprised if the casinos actually made money from errors overall. If anyone in casino management has another point of view then I’m all ears to hear it.