18%: The average tip Americans leave for "good service."
7 of 10: Number of diners who tip 15 to 20 percent for "good service."
1 of 10: Number of diners who tip more than 20 percent for "good service."
26%: The number of Midwesterners who tip 15 percent or under, the highest in the nation. That's compared with 24 percent in the West, 22 percent in the South and 15 percent in the Northeast.
and …
Diners become more generous as they age, and there's a bit of a gender gap, too; in general, men tip higher than women.
Source: June 2014 survey of more than 2,000 diners conducted by Harris Poll.
One more study: A less scientific survey, also from 2014, analyzed millions of credit card transactions (taken primarily but not exclusively from restaurants) from the payment service Square. That study placed the nation's average tip amount at 16.1 percent. In this study, Minnesota consumers averaged a tip amount of 15.7 percent.
