We propose that when boys are relatively better in science and mathematics while girls
are relatively better at reading than other academic areas, there is the potential for substantive sex
differences to emerge in STEM-related educational pathways. The differences are expected
based on expectancy value theory and are consistent with prior research (Eccles, 1983; Wang &
Degol, 2013). The differences emerge from a seemingly rational choice to pursue academic paths
that are a personal strength, which also seems to be common academic advice given to students,
at least in the UK (e.g., Gardner, 2016; Universities and Colleges Admissions Service [UCAS],
2015).
The greater realization of these potential sex differences in gender equal nations is the
opposite of what some scholars might expect intuitively, but is consistent with findings for some
other cognitive and social sex differences (e.g., Lippa et al., 2010; Schmitt, 2015). One
possibility is that the liberal mores in these cultures, combined with smaller financial costs of
foregoing a STEM path (below), amplify the influence of intra-individual academic strengths.
The result would be the differentiation of the academic foci of girls and boys during secondary
education and later in college, and across time increasing sex differences in science as an
academic strength and in graduation with STEM degrees.
Whatever the processes that exaggerate these sex differences, they are abated or
overridden in less gender equal countries. One potential reason is that a well-paying STEM
career may appear as an investment in a more secure future. In line with this, our mediation
analysis suggests that OLS partially explains the relation between gender equality and the STEM
graduation gap. Some caution when interpreting this result is needed, though. Mediation analysis
depends on a number of assumptions, some of which can be tested using a sensitivity analysis,
which we conducted (Imai, Keele, & Yamamoto, 2010). The sensitivity analysis gives an
indication of the correlation between the statistical error component in the equations used for
predicting the mediator (OLS) and the outcome (STEM graduation gap); this includes the effect
of unobserved confounders. Given the range of rho values in the sensitivity analysis (Fig. S1), it
is possible that a third variable could be associated with OLS and the STEM graduation gap. A
related limitation is that the sensitivity analysis does not explore confounders that may be related
Gender Equality Paradox – 16
to the causal variable (i.e., GGGI) and the mediator variable. Future research that includes more
potential confounders is needed, but are currently unavailable for each of the countries included
in our analyses.