A new U.S. Department of Commerce study finds that “women are vastly underrepresented in science, technology, engineering and math (STEM) jobs and among STEM degree holders despite making up nearly half of the U.S. workforce and half of the college-educated workforce.” Interestingly, the study reports that the female share of all STEM jobs in 2009 was exactly the same as in 2004 at 24 percent, and the share of jobs held by women in the field of “computer science and math” actually fell from 30 percent in 2000 to 27 percent by 2009.

To explain the stubborn underrepresentation of women in STEM jobs and majors, the Department of Commerce cites three main factors: a) a lack of female role models in STEM fields, b) gender stereotyping, and c) less family-friendly flexibility in STEM fields compared to other occupations. In the conclusion of the report, the Department of Commerce is very clear about its ultimate, long-term goal: perfect gender parity in STEM.

Unfortunately, the Commerce report never addressed what might actually be the most important reason that females remain persistently underrepresented in STEM jobs and college majors, even after decades of concerted effort and federal funding targeted to change that outcome: the continuing and statistically significant gender disparity in mathematical aptitude favoring males.

The chart above shows average test scores by gender on the College Board’s math SAT test, which is taken annually by more than a million college-bound high school seniors. High school boys have scored higher on average than their female counterparts on the SAT math test in every year from 1972 to 2010, and the differences are statistically significant and large, averaging 38 points higher for boys over the last four decades. At the very high end of mathematical ability, high school boys overwhelmingly outnumber girls by a ratio of more than 2:1 for perfect test scores of 800 points on the math SAT test.

Bottom Line: Given the significant gender differences in mathematical aptitude favoring high school boys that have persisted over many generations on standardized tests like the math SAT, it’s perfectly understandable that males are overrepresented in STEM jobs and college majors. Here’s the stark reality overlooked by the Commerce study: Unless and until we see perfect gender parity on standardized math tests like the SAT, we shouldn’t expect to see perfect gender parity in STEM fields. As long as there are such consistently large gender differences in mathematical ability based on the math SAT test, the goal of gender parity in STEM field is unrealistic, unwarranted, and unreachable.