Countries with Higher Levels of Gender Equality Show Larger National Sex Differences in Mathematics Anxiety and Relatively Lower Parental Mathematics Valuation for Girls

Despite international advancements in gender equality across a variety of societal domains, the underrepresentation of girls and women in Science, Technology, Engineering, and Mathematics (STEM) related fields persists. In this study, we explored the possibility that the sex difference in mathematics anxiety contributes to this disparity. More specifically, we tested a number of predictions from the prominent gender stratification model, which is the leading psychological theory of cross-national patterns of sex differences in mathematics anxiety and performance. To this end, we analyzed data from 761,655 15-year old students across 68 nations who participated in the Programme for International Student Assessment (PISA). Most importantly and contra predictions, we showed that economically developed and more gender equal countries have a lower overall level of mathematics anxiety, and yet a larger national sex difference in mathematics anxiety relative to less developed countries. Further, although relatively more mothers work in STEM fields in more developed countries, these parents valued, on average, mathematical competence more in their sons than their daughters. The proportion of mothers working in STEM was unrelated to sex differences in mathematics anxiety or performance. We propose that the gender stratification model fails to account for these national patterns and that an alternative model is needed. In the discussion, we suggest how an interaction between socio-cultural values and sex-specific psychological traits can better explain these patterns. We also discuss implications for policies aiming to increase girls’ STEM participation.

• Using a train timetable to work out how long it would take to get from one place to another • Calculating how much cheaper a TV would be after a 30% discount • Calculating how many square metres of tiles you need to cover a floor • Understanding graphs presented in newspapers • Solving an equation like 3x+5= 17 • Finding the actual distance between two places on a map with a 1:10 000 scale • Solving an equation like 2(x+3) = (x + 3) (x -3) • Calculating the petrol consumption rate of a car Students indicated to what degree they agreed with these statements on a 4-point scale. This variable was not available for all students. For the 2003 PISA data, the availability of a mathematics self efficacy score per country ranged between 95% and 100%, and for the 2012 PISA data between 55% and 67%. 1 The PISA databases of 2003 and 2012 provide a standardized variable SCMAT expressing mathematics self-concept based on 5 statements (OECD, 2014, p.323).
• I am just not good at mathematics • I get good in mathematics • I learn mathematics quickly • I have always believed that mathematics is one of my best subjects • In my mathematics class, I understand even the most difficult work Students indicated to what degree they agreed with these statements on a 4-point scale. This variable was not available for all students. For the 2003 PISA data, the availability of a mathematics self concept score per country ranged between 95% and 100%, and for the 2012 PISA data between 55% and 67%. Thus, while national averages of mathematics anxiety relate strongly to HDI and GGI (the higher the level of development, the lower the national level of mathematics anxiety), the relation is weaker for self efficacy and not found for self concept.

Relation between self efficacy and mathematics performance
There was a positive correlation between mathematics performance and self efficacy in 2003, r(39)=.45,p=.003, and in 2012, r(66)=.60, p<.001.
The correlation between mathematics performance and self concept was weaker in 2003, r(39)=-.26,p=.09, and in 2012, r(59)=-.32,p=.006. Thus, national averages of self efficacy are positively correlated with math performance, whereas the opposite is true for self concept. The finding is that higher levels of mathematics performance are associated with lower levels of self concept. This is not a new finding, though (Stevenson et al., 1990). When looking at the self-concept questions (above), it is obvious that the better schools and classes are, the less likely students will answer, for example, that they even understand the most difficult work.

Sex differences in mathematics efficacy and self concept
Overall levels of mathematics efficacy were higher in countries with higher mathematics performance. A random intercept model (similar to that in the main manuscript) shows that this relation was stronger for boys than for girls (for 2012: β=-0.0011,p<.001, for 2003: β=-0.0013,p<.001). Further, overall levels of self concept were lower in countries with higher mathematics performance. Here too, the random intercept model shows that this effect was stronger for boys than for girls (for 2012: β=0.0014, p<.001, for 2003: β=-0.0015,p<.001).
Similar to mathematics anxiety, there were significant sex differences (boys scoring higher) in both mathematics efficacy ( In the main paper, we adjusted mathematics anxiety for mathematics performance by subtracting the normalized scores of both variables for each student. We carried out the same calculation for mathematics efficacy and self concept. Following this calculation, we found the adjusted international average sex difference in self efficacy was 0.23 sd in 2003 and 0.18 in 2012. Similarly, the adjusted international average sex difference in mathematics self concept in 2003 was 0.20 sd and 0.18 sd in 2012.

Power distance
In the main manuscript, we reported that power distance was correlated with national levels of mathematics anxiety. We did not find such a correlation for mathematics efficacy, but we found a link for mathematics self concept in 2012, r(51)=-.28, p=.04 (see Table S1 for all correlations). Similar to the analysis of variance testing testing the relation between mathematics anxiety and single/mixed sex schooling, the interaction between gender and type of school was not significant for either mathematics efficacy or self concept.

Parental valuation
In the main manuscript, it was shown that the larger the sex difference in mathematics anxiety, the larger the sex difference in students' perception of parental valuation. The same effect was found for self efficacy, r(66)=0.57, p<.001, and for self-concept, r(66) =0.35,p<.01. This effect is weaker or non-existent when the performance-adjusted scores are used (mathematics efficacy, r(66)=0.36,p<.01 ; self concept, r(66)=.10, p=.43).

Details of categorization of parental occupation used in main manuscript
In the main manuscript, we use the proportion of fathers to mothers working in Science, Technology, Engineering, and Mathematics (STEM) occupations. PISA does not categorize occupations as STEM, and we have therefore classified all 586 listed occupations as either "definitely a STEM occupation" and those that are not.
We considered the following 65 as "definitely a STEM occupation": Agricultural and industrial machinery mechanics and repairers, Air conditioning and refrigeration mechanics, Aircraft engine mechanics and repairers, Aircraft pilots and related associate professionals,