A new report from Cornell School of Hospitality Administration, called, "Race Differences in Tipping: Questions and Answers for the Restaurant Industry,†finds that there are a number of differences in how people of different races, genders, and geographic location tip wait staff, and that members of the groups that normally don't tip as well may get worse service as a result. Here's the press release (you also can get the full PDF of the study, which is pretty interesting, from the site, but free registration is required). For the research part, it basically found that those who are white, 40 to 60 years old, live in urban areas, live in the Northeast, and are highly educated are most likely to be better tippers than people who are non-white, live in rural areas, etc. The study's author believes this disparity can be countered by educating all diners about the norms in tipping (i.e., 15 percent to 20 percent of the bill), and once everyone knows the norms, they'll tip according to the norms, and servers will treat everyone equitably.
I'm not sure what to make of all this. Back in my server days, I was regularly suprised when the conventional wisdom (a group of women won't tip well, celebrities will tip hugely, etc.) was wrong, and learned pretty quick to just try to give my best to everyone. Sometimes you'll be rewarded, sometimes you won't. But service shouldn't depend on the tip you anticipate getting (unless, of course, it's a regular big-tipper. Sorry, those folks will always get special treatment).