In a study conducted in Pennsylvania, servers in various restaurants wrote Thank you on randomly selected bills before presenting the bills to their customers  Tips on these bills were an average of three percentage points higher than tips on bills without the message
Ttherefore, if servers in Pennsylvania regularly wrote Thank you on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been
Regularly seeing Thank you written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.