(Guest Post by Gema Zamarro & Lina M. Anaya)
Employment in the so-called STEM (Science, Technology, Engineering and Mathematics) fields is projected to continue growing according to the Bureau of Labor Statistics. Additionally, wages in STEM field occupations are estimated to be on average nearly double the national average of wages for non-STEM jobs. Despite this promising future, women continue to be under-represented in STEM. Women are less likely to enroll in STEM degrees in college and represent a smaller share of STEM occupations. The question is why? Only after understanding the possible sources of such gender gaps we can have an idea of what can be done about it.
This question has haunted me (Gema) since my daughter, then a kindergartener, came home one day saying a boy in her class told her “girls are not good in math.” Indeed, researchers have pointed out at gender differences in math performance and math perceived ability as possible drivers of later gender gaps in STEM. I wondered if parents could somehow counter these effects. After all, my previous work indicated that parental occupation type could be important for women’s long term STEM outcomes. In a recent working paper, I partnered with Lina M. Anaya, a Ph.D. student at the Department of Education Reform at the University of Arkansas, and Frank Stafford, Economics professor at the University of Michigan, to try and shed some light on these questions, using data from the Panel Study of Income Dynamics (PSID).
Using information from the multiple supplements of the PSID, we measured gender gaps in performance on the standardized Woodcock Johnson Applied problems test (W-J AP) and self-reported perceived math ability, measured on children from PSID families when they were between 6 and 17 years old (on average around 11 years old). Then, we are able to track these children and study their likelihood of majoring in a STEM field in college. We found that boys are more confident in their abilities than is warranted by their performance, while girls are less confident than is warranted by their performance. But the problem isn’t just one of lack of confidence — boys’ confidence contributes more to their pursuit of STEM majors than girls’ confidence, even if they had the same true ability and same level of confidence.
Our results corroborated significant gender differences in W-J AP test performance and in perceived math ability during childhood. Even after conditioning in a given level of math performance in the W-J AP test, girls reported significantly lower levels of perceived math ability than boys (See Table 1). In the highest percentiles of math performance, 64% of boys reported the highest levels of perceived math ability, as compared to 50% of the girls. Even in the lowest levels of math performance, boys tended to be more optimistic with respect to their math ability, 29% of the boys reported the highest levels of perceived math ability, relative to 17% of the girls doing so. Having a parent with an occupation in STEM helped increase math performance but did not seem to help improve perceived math ability, if anything it seemed that those with parents in science were more pessimistic.
Table 1: Perceived Math Ability by Gender, given W-J AP scores (% of sample)
| Perceived Math Ability | ||||
| W-J AP (percentile) | Gender | 1 to 3 | 4 to 5 | 6 to 7 |
| 0-50 | Boys | 15.9% | 55.1% | 29.0% |
| Girls | 18.7% | 64.2% | 17.1% | |
| 51-80 | Boys | 4.1% | 44.3% | 51.6% |
| Girls | 6.5% | 49.9% | 43.6% | |
| 81-100 | Boys | 2.8% | 32.7% | 64.4% |
| Girls | 4.6% | 45.2% | 50.2% | |
Note: Weighted percentages reported using child population weights
Interestingly, girls’ lack of perceived ability seems to be something specific to math and not the result of girls generally reporting lower levels of perceived ability. The PSID also included results in the Woodcock Johnson reading test (W-J reading) and asked kids to report on their perceived ability in reading. We use this information to study perceived ability in reading conditional on performance. As it can be seen in the results in Table 2, gender patterns are very different for reading, a subject where girls, on average, outperform boys. In this case, we observe smaller gender differences of perceived reading ability among those scoring in the higher percentiles of the W-J reading test while girls performing in the lower percentiles report higher levels of perceived ability than boys.
Table 2: Perceived Reading Ability by Gender, given W-J reading scores (% of sample)
| Perceived Reading Ability | ||||
| W-J Reading (percentile) | Gender | 1 to 3 | 4 to 5 | 6 to 7 |
| 0-50 | Boys | 13.4% | 57.8% | 28.8% |
| Girls | 9.2% | 50.1% | 40.7% | |
| 51-80 | Boys | 4.3% | 47.1% | 48.6% |
| Girls | 3.4% | 32.4% | 64.1% | |
| 81-100 | Boys | 1.9% | 29.5% | 68.6% |
| Girls | 1.5% | 33.5% | 65.0% | |
Note: Weighted percentages reported using child population weights
Finally, since the PSID tracked these kids, we study to what extent math performance and perceived math ability, during childhood, and parental occupation type are related to the probability of majoring in STEM during college. Overall, as expected, we find that women are less likely to major in STEM in our sample, especially when we look at the so called “hard sciences” fields of engineering, architecture, mathematics and computer sciences. Both higher levels of math performance in the W-J AP test and higher levels of perceived math ability are related to higher probabilities of majoring in a STEM field.
But, here is where it gets interesting, the effects of higher levels of math performance and perceived ability are much bigger for boys than for girls. Performing in the highest percentiles of the W-J AP distribution, as compared to performing in the lowest percentiles, is associated with an increase in the probability of majoring in a “hard sciences” STEM field of about 13 percentage points for boys but only 6 percentage points for girls. Similarly, reporting the highest levels of perceived math ability, as compared to the lowest levels, is associated with an increase in the probability of majoring in a “hard sciences” field of about 7 percentage points for boys but only 2 percentage points for girls. These results suggest a loss of STEM enrollment by otherwise capable women. And we can’t simply fix the problem by trying to boost women’s confidence in their true abilities, because women’s confidence contributes less to pursuing STEM than men’s confidence. Perhaps men are rewarded for over-confidence in a way that women are not.
Interestingly, having a parent who works in a STEM occupation could help girls and not so much boys. The probability of majoring in “hard sciences” STEM fields increases by about 14 percentage points for girls when one of the parents works in a science job. For boys the increase of this probability is only 4 percentage points. Whatever the reason, these results suggest that parental occupation type could be an important factor reducing gender differences.
As for the answer I gave to my daughter, I said “It is not true that girls are bad at math. Look at your mother. My job is doing math all day!” I work on the field of applied econometrics and so, I guess that was close enough.
Jay P. Greene's Blog 
I think I’ve said this here before, but I’ll say it again.
In 22+ years of teaching secondary math, girls consistently outperform boys in my 8th grade class, but I have more boys who pursue STEM-related fields as college students/adults than girls. Something is happening between the age of 14-18 to my stellar girl students; while many of them go on to college/careers, something is taking them on a path away from STEM. I suspect the ‘girls don’t do math/science’ message affects their perception more than I hope, as this study seems to suggest.
Because it could not possibly be that girls/women are more interested in working with people. BTW, I have two close male relatives, both highly talented in math, who left successful engineering careers to work in people-oriented fields. Girls just do it more often.
My career path was similar to your relatives; engineering-degreed R&D nerd for USAF, turned teacher. The most successful engineers, successful meaning handed more responsibility, had to work well with people. I suspect that just as I’ve had students tell me ‘You were the best math teacher I’ve had’ their HS teachers aren’t demanding enough or encourage the women enough to grow their STEM talent/desire, thus it withers.
How does the fact that girls, on average, tend to be better readers and writers than boys get factored in? Are boys told that they are better in math because girls are better in reading and writing?