Differences in both grade average and variability between boys and girls are smaller in STEM than non-STEM subjects, according to a study in Nature Communications. The authors suggest that greater variability in grades among boys is therefore insufficient to explain male over-representation in STEM.

Fewer women than men pursue careers related to Science, Technology, Engineering, and Mathematics (STEM), even though girls consistently outperform boys at school in these subjects. One proposed explanation for this is that there is more variability in terms of academic ability among boys than girls. According to this ‘variability hypothesis’, even though girls do better than boys on average, more boys excel in STEM subjects, and those who excel are more likely to choose a STEM career.

Rose O’Dea and colleagues combined the results of 227 studies on teacher-assigned school grades for over 1.6 million students to compare differences in academic grades between boys and girls. They found that differences in the variance of grades between boys and girls are smaller in STEM than in non-STEM subjects, such as English and History. Simulations of these differences suggest the top 10% of a class contains equal numbers of girls and boys in STEM, but more girls in non-STEM subjects. The authors argue that although boys show greater grade variability than girls, this alone cannot explain why men are specifically over-represented in STEM.