evidence: Joe Biden: "For four years, I was a full professor at the University of Pennsylvania." [...] Biden served as Benjamin Franklin Presidential Professor of the Practice at the University of Pennsylvania between his tenure as vice president and the start of his presidential campaign. However, the duration of the position was closer to two years than four, since he was on leave while running for president. Also, his duties might not conform to the full range of activities that the public might associate with the term "full professor," including teaching semester-long classes, conducting independent research, and handling administrative responsibilities. [...] Biden said, "For four years, I was a full professor at the University of Pennsylvania."