Interesting.
The difference between Delaware, 21.8%, on the high end and California, 17.5%, at the bottom isn't really a whole lot.
And one flaw in the study is that it only considered credit card or other electronic tips. I will often times pay with a credit card but leave a tip in cash. My purchases like that would have been counted as zero tip in this survey. Maybe Californians are more like to leave cash tips?
Utah faired better than I had expected, 19.2%, near the middle. When I was younger Utahans were notorious for leaving very small or no tips, looks like that has changed.
I don't like our tipping system, I would prefer knowing the wait staff were adequately paid. You could still leave the occasional tip for truly outstanding service, but not to make sure you weren't starving someone. Even so I tip fairly generously because I know many wait staff depend on tips for most of their earnings.