We have heaps of information showing a gender pay gap. What we know less about how this could factor into women's decisions to pursue graduate degrees, which would tend to net a lower return on investment than their male counterparts.

Researchers at Yale University aim to answer that question in a new paper by looking at the return on investment for men and women heading to medical school. They find that -- in strictly financial terms -- a female (but not male) primary care doctor would have been better off not heading to medical school, and instead pursuing a less-costly degree and becoming a physician's assistant.

Both men and women earn more as primary care doctors as they do as physician assistants. But there's a big difference in how much more. Researchers M. Keith Chen and Judith Chevalier estimate that the median man in their sample who has worked 10 years as a primary care doctor earns a premium of "over $25 per hour as a physician rather than as a PA with 10 years of experience." For women, however, that number hovers around $16."

But a lot of it actually has to do with something completely different: The number of hours that each gender works.The study finds that, on average, male primary care physicians works 11 hours more per week than their female counterparts.

"The importance of these results is not necessarily in finding that the median woman physician would have been better off becoming a PA," Chen and Chevalier conclude. "Rather, it's important to recognize that a large number of female physicians are working few enough hours that the financial payback on their educational investments is doubtful."

Physician assistant, despite the-less-than-impressive title, is actually a position that pretty strongly resembles that of a primary care doctors. In many states, they have the authority to diagnose and treat illnesses without a sign off from a physician. The degree program, however, is significantly shorter: Usually about 26 months, compared to four years of medical school followed by residency. That makes the tuition for a physician assistant program significantly less expensive than the investment needed for a medical degree.

(h/t Christopher Shea)