Why do new female college grads earn 17% less than men?

May 16, 2011, 2:26 PM UTC

By Anne Fisher, contributor

FORTUNE — If you’re a woman about to graduate from college (or have a daughter who is), the National Association of Colleges and Employers has some disconcerting news for you.

First, the bright side: You probably won’t have more trouble finding a job than the guy sitting next to you. In almost every year since 1994, unemployment among female grads has been lower than for their male counterparts. In 2010, it was 8.1% for women, versus 10.3% for men.

Great, but here’s the rub: Even if you snag the exact same job as your male classmate, you’ll probably get paid 17% less.

At least, that’s what happened last year. NACE research director Ed Koc analyzed starting salaries of 2010 bachelor’s degree graduates and found that women pulled down an average of $36,451, vs. $44,159 for men.

You might suppose that’s a result of men choosing majors that lead to higher-paying jobs. But the NACE study found that men usually come out ahead even in the same fields. One exception: Engineering. Because only about 18% of engineering grads are female, women engineers “are highly sought-after ‘commodities’ and command a premium price,” NACE reports.

That’s not the case in other fields. Women earning degrees in computer science are scarce too — also about 18% of all new entrants to the field last year. Yet their 2010 starting pay averaged $52,531, while men earned $56,227.

Oddly, the gap gets even wider in careers where women dominate. Consider, for example, education, where about 80% of new grads are female. Average starting pay: $29,092. Average starting pay for men with education degrees: $39,849.

What gives?

“Women don’t negotiate their pay when hired, as if they’re happy just to get the job,” observes Marcia Reynolds, a Phoenix-based executive coach whose clients include AT&T (T), American Express (AXP), and Ernst & Young. Getting paid the same as the guys “takes a little time researching average male hiring salaries in the field you’re entering. It also takes knowing how to promote yourself.”

In her coaching work, Reynolds has noticed time after time that women are too modest for their own good.

“They don’t like to self-promote. When I ask my female executive clients to identify what they contribute [to the organization], beyond their technical skills and knowledge, they act as if I’m speaking another language,” Reynolds says.

Reynolds’ book, Wander Woman: How High-Achieving Women Find Contentment and Direction, addresses this issue head-on, and describes some self-promotion exercises that women right out of college might consider practicing. First, make a list of “what traits you possess that have helped drive your success so far.”

Can’t come up with anything that makes you stand out from the crowd? Try sounding out your fans, whether they are professors, peers, or that boss who raved about your work at your last internship.

“When someone tells you, ‘You did a great job,’ don’t just say, ‘It was nothing,’” says Reynolds. “Ask them specifically what they thought you did. Let others help you identify your strengths.”

Pinpointing their competitive advantage, and then talking it up, “has helped women not only get jobs, but get special projects and promotions once they’re hired,” Reynolds adds.

For newly minted college grads, it may also help lead to equal pay.