A Yahoo article referencing a Payscale study (how circular could I get with this if I really tried?) says that if you’re still tipping your restaurant server 15%, then you’re below the norm and too darned cheap. I posit that this could be an example of declining math skills in the U.S. populace. It’s much easier to mentally double your bill and move the decimal point over than it is to actually attempt to calculate 15% of your bill. And on larger parties, the house will often add a gratuity of 18% onto the bill, which some patrons don’t notice and then tip again, thus driving the average tipping amounts even higher.
I normally tip about 20% when the service is anything better than adequate. Part of this is the laziness of not wanting to try to do math in my head (but I could if I wanted to -really!) and part is due to the fact that my mother and sister spent a good deal of the their adult work lives waitressing. I know how hard restaurant servers work and just how much that extra bit of income can mean to someone on the lower levels of the working class.
So, okay, maybe I should give my fellow diners the benefit of the doubt and agree that we have become more generous on the whole. But I still think that math thing has a lot to do with it.