Bis in die 60er Jahre hinein siezten sich schon 16- bis 17-Jährige gegenseitig als Zeichen ihres Status als junge Erwachsene. Until the 1960s, even 16- and 17-year-olds said Sie to each other, as a sign of their status as young adults. This is reported in a 2008 article in the magazine bild der wissenschaft. It was the students of the 1960s, the article says, who brought the du out of the family and made it socially acceptable again. According to the linguist Leonhard Kretzenbacher, the age difference between two speakers matters more for the form of address than their absolute age.