Share of top-performing students

The estimates are based on Hanushek and Woessmann's combination of scores from international student achievement tests. Top students are those that reach a levelequivalent to 600 test-score points on the PISA scale (above one standard deviation of the average student in an OECD country). The estimates are not given for aparticular year, but instead are based on all standardized math and science test scores each country participated in.