Pay equity between men and women has been a hot topic in Washington as of late, and this should add fuel to the fire: a new study reveals female doctors are being paid less than their male counterparts.

Researchers at the University of Michigan in Ann Arbor sent questionnaires to 800 physician-researchers and found that the women earn an average of $12,000 less per year than men do, even after accounting for their work hours and area of specialty.

“Disturbingly, even after we controlled for all those other factors, we found that male doctors were paid more than female doctors for doing the same work,” said Dr. Reshma Jagsi, the study’s lead author.

So why does it happen? The researchers said women might be less aggressive when negotiating pay, or they may be willing to take a lower salary in exchange for less on-call time and more schedule predictability. But Jagsi worries there could also be unconscious biases in hiring and pay.

Regardless, the pay disparity is very real, and researchers calculated that the average female doctor-researcher would make about $350,000 less over the lifespan of her career than a man doing similar work because of the unexplained salary differential.