This chart shows the percentage of male and female students who received a given grade in introductory economics course who then later majored in economics. Data refer to an anonymous research institution, from a study by Harvard Professor Claudia Goldin. (Claudia Goldin/Harvard University)

A message to the nation’s women: Stop trying to be straight-A students.

No, not because you might intimidate easily emasculated future husbands. Because, by focusing so much on grades, you might be limiting your earning and learning potential.

The college majors that tend to lead to the most profitable professions are also the stingiest about awarding A’s. Science departments grade, on a four-point scale, an average of 0.4 points lower than humanities departments, according to a 2010 analysis of national grading data by Stuart Rojstaczer and Christopher Healy. And two new research studies suggest that women might be abandoning these lucrative disciplines precisely because they’re terrified of getting B’s.

Claudia Goldin, an economics professor at Harvard, has been examining why so few women major in her field . The majority of new college grads are female, yet women receive only 29 percent of bachelor’s degrees in economics each year.

Goldin looked at how grades awarded in an introductory economics class affected the chance that a student would ultimately major in the subject. She found that the likelihood a woman would major in economics dropped steadily as her grade fell: Women who received a B in Econ 101, for example, were about half as likely as women who received A’s to stick with the discipline. The same discouragement gradient didn’t exist for men. Of Econ 101 students, men who received A’s were about equally as likely as men who received B’s to concentrate in the dismal science.

Another research project, led by Peter Arcidiacono at Duke University, is finding similar trends in science, technology, engineering and mathematics.

These STEM majors, as with economics, begin with few women enrolling and end with even fewer graduating. This “leaky pipeline” has been somewhat puzzling, Arcidiacono said, because women enter college just as prepared as men in math and science. On average, women more eagerly spend time studying than men do, a trait that should theoretically attract women to STEM fields, which generally assign more homework.

Plenty has been written about whether hostility toward female students or a lack of female faculty members might be pushing women out of male-dominated majors such as computer science. Arcidiacono’s research, while preliminary, suggests that women might also value high grades more than men do and sort themselves into fields where grading curves are more lenient.

It’s not clear from the data why women might be more sensitive to grades than men are.

“Maybe women just don’t want to get things wrong,” Goldin hypothesized. “They don’t want to walk around being a B-minus student in something. They want to find something they can be an A student in. They want something where the professor will pat them on the back and say ‘You’re doing so well!’ ”

“Guys,” she added, “don’t seem to give two damns.”

So maybe the better question is: Why aren’t men scared off by rigid grading curves?

Male students could be more overconfident — effectively, college bros shrug off gentleman’s C’s (or, more often today, gentleman’s B’s) as unrepresentative of their true brilliance.

Or maybe men have their “eyes on the prize,” in Goldin’s phrasing.

U.S. college graduates with STEM and economics degrees have among the highest median salaries. Men might be more likely to see themselves as future breadwinners and persevere in studies that are likely to maximize their earnings — come hell or high water or B-minuses.

Of course earning potential isn’t the only — or even most — important factor in choosing a discipline. (Art History Mob, please don’t come after me, too!) Intellectual fulfillment and passion count a lot.

But I fear that women are dropping out of fields such as math and computer science not because they’ve discovered passions elsewhere but because they fear delivering imperfection in the “hard” fields that they (and potential employers) genuinely love. Remember, on net, many more women enter college intending to major in STEM or economics than exit with a degree in those fields. If women were changing their majors because they discovered new intellectual appetites, you’d expect to see greater flows into STEM fields, too.

Colleges have a role in helping women realize that quantitative fields are within their reach. Administrators might try to reduce the grading differential between humanities and STEM fields or provide better support systems for women who get discouraged.

But women must also change their myopic attitudes about the significance of grades.

Women, admirably, want to excel — and usually do, academically. We earn, on average, higher grades than men in almost every subject. (Partly, presumably, because women seem to disproportionately take classes we know we’ll do well in.) But if women want to compete with the big boys, in the disciplines and professions where men continue to dominate, we need to overcome our B-phobia. Rinse yourselves of the intoxicating waters of Lake Wobegon, ladies, and embrace meaningful mediocrity.

Catherine Rampell, a former economics reporter for the New York Times, will write a twice-weekly column for The Post.