A new study released Thursday by PayScale, an online resource for salary and benefit information, puts the average gender pay gap—when controlled for factors such as education, geography, industry and work experience—at 2.7%. But when you focus in on the disparity between married men with kids and married women with kids, that gap widens to 4.2% (a controlled median pay of $67,900 per year for men, vs. $65,000 for women).

This disparity is a result of long-standing gender biases and social expectations, says Ken Matos, the senior director of research for the Families and Work Institute. He says that the difference in salary can be attributed, at least in part, to the common perception that having children hurts women’s ability to succeed at work—a belief that’s rarely extended to dads.

When supervisors believe that motherhood limits women’s abilities at work, he says, “whether or not they’re actually doing their job really well gets lost” in that perception.

PayScale compiled data from 1.4 million full-time employees, using information gathered form July 2013 to July 2015.

The study also revealed:

Men’s salaries continue to rise into their 50s, while women’s wages peak much earlier.

Men hit a peak median salary of $75,000 per year somewhere between age of 50- 55. Women, on the other hand, see their salaries begin to stagnate between the ages of 35 and 40, when they reach a median of $49,000 per year.

More education only exacerbates the gender gap.

Though women tend to be more educated than men, the study suggests that schooling actually increases the wage disparity. PayScale found a 4.6% wage gap between male and female MDs and a 4.7% gap between MBA holders. The largest differential? PhDs, with a gender pay of 5.1%.

Men are more likely than women to say they prioritize work and family obligations.

A full 52% of men reported that put home life before work one to two times per month, compared with 46% of women.

“Women are very hesitant to admit when they have a home obligation that takes priority over work, because we seem to be more penalized for it in our pay,” says Aubrey Bach, the marketing manager for PayScale.

While sorting through the numbers can be depressing, Matos says that understanding the nuances of the gap is an important step toward closing it.

“What’s important about these studies — breaking it down into more complex pieces than just man vs. woman — is that it allows you to think about where we can intervene to make it possible for both men and women to advance their careers together,” he says. “We’ve exhausted what we can do with just focusing on women. Now we need to do the next stages, which are dealing about the assumptions of men and what they should be doing.”

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