Old People and Foreigners

Since I've been working as a server at Chili's (I love it, and it's been great... if you're wondering), I have noticed that when it comes to the "Older Generation" and the "Foreigners" they aren't as knowledgeable in the tipping department. I give out great service and I know they recognize that, but for some reason they still think that 10% is the tip amount. Do they realize that I am making $3.75 an hour?! Chris and I went to this Japanese restaurant and on the bill at the bottom they put what a 15% tip and a 20% tip would be! Genius! I wish Chili's would invest, then I might be able to afford those slip covers I want!