Discontinuity tells

A particular pattern in the numbers, a misbehaviour which shows that the scale is more than just a record: Source: Reddit Distribution of results of the Matura (high school exit exam) in Poland in 2013. The minimum score to pass is 30%. Commentary: Unusual distributions of scores on final high-school exams in Poland. But let’s be clear — this is not about Poland. The x-axis pretends to innocence, just a passive measure of how the data fall. This pattern, though, the cratering before the threshold and then the pile-up just after, show that the threshold itself has a distorting effect. Here’s data on the New York high school exit exam Source: Dee, T. S., Dobbie, W., Jacob, B. A., & Rockoff, J. (2019). The causes and consequences of test score manipulation: Evidence from the New York regents examinations. American Economic Journal: Applied Economics, 11(3), 382-423. (NBER working paper 22165). There is some discretion in the exam marking. The grade matters to what happens to the students…