When new PISA data are published, many researchers around the world analyse them with the aim of shedding light on all sorts of questions. One question in search of an answer: why are women under-represented in science, technology, engineering and mathematics (STEM) professions? Using data from the Program for International Student Assessment (PISA), Gijsbert Stoet and David Geary examined the nature of the gender gap in STEM fields. The authors analysed data from 67 countries and economies participating in the 2015 cycle of PISA; these data were supplemented by country-level indicators on gender equality (the Global Gender Equality Index) and the proportion of women graduating in a STEM field. Their analysis yielded an interesting result.