one of the outstanding differences is the retirement age. american professors can remain active as long as they want, while korean professors are legally required to retire at age 65. despite the advantage of being a life-time professor, some american professors volunteer to retire when they reach 70 or so. i once asked an eminent american professor who had retired at 75, “what made you decide to retire?” “young students are no longer interested in literature these days,” he answered. “so i lost interest in teaching them as well. besides, i do not want to be evaluated by them every semester at this age. they are younger than my grandchildren.” a few days ago, i asked another famed american professor emeritus the same question, “why did you decide to retire?” “i’m 71. i’m older than the grandfathers of my students,” he chuckled. “that’s not good. besides, i couldn’t grade 70 students. i fell asleep while grading. so i decided to retire.”