Incentives – Grading On A Curve

Tim Harford is an economist who has a newspaper column called “The Undercover Economist”. He presents tongue-in-cheek answers to a wide variety of questions from readers. In his book, “Dear Undercover Economist,” some of his favorite responses have been collected together. Two that really tickled me were related to the practice of grading on a curve.

The first was from a student, complaining that their economics lecturer was grading them on a curve. Since the number of students getting A’s or D’s would be the same, no matter what the average performance of the class, the student pointed out that they could all slack off, if only they would all slack off. How, though, could they make sure that everyone pulled together to avoid studying?

Tim Harford gave a tongue-in-cheek answer – act like a stereotypical student body. That is,

  • Identify nerds, geeks and study-freaks and punish them.
  • Organise events that discourage study (parties, etc).
  • Make sure people share their notes, so that if some students do pull ahead, they pull everyone with them, leaving them no reward – no incentive – for their hard work.

The next week, apparently, the students’ professor wrote in, complaining that his students had formed a “let’s not work” cartel, and asked advice on how to break it up. Tim Harford gave a tongue-in-cheek answer – act like a stereotypical awful lecturer.

  • To prevent the cartel from identifying studious students, there should be no continuous assessment, just one whopping great big exam.
  • To minimise the value of note-sharing, and maximise the value of individual study, ensure the exam tests students on obscure points only to be found hidden inside an enormously long book list.

There were other points. Tim’s answers are really quite funny. In all seriousness, he accepts grading on a curve as a given and explains

  • For students, the logical consequences of this grading policy is to form a cartel and slack off
  • For lecturers, the logical consequence of the students’ cartel is to become an awful lecturer.

I recommend getting the book (though I enjoyed this one even more). I guess the real lesson from his examples is that grading on a curve is not such a hot idea. The logical response to it is not at all like we hope students and teachers will behave!