Women physicians are substantially less likely to be full professors than men of similar age, experience, specialty and research productivity.

With recent increases in the number of attending , women now comprise nearly half of all new physicians. But the proportion of women at the rank of fullprofessor at U.S. medical schools has not changed since 1980, despite efforts to increase equity, according to a new research study led by Anupam Jena, associate professor of at Harvard Medical School. The results are published today in JAMA.

"Many people have opinions about why women in medicine are less likely to be promoted than men," said Jena, who is also a physician at Massachusetts General Hospital. "We're trying to separate fact from conjecture by using detailed data."

Taking advantage of a database from Doximity, a commercial social networking service for physicians containing professional data from more than a million doctors and more than 90,000 U.S. medical school , the researchers were able to analyze data from state licensing boards, Pub Med and other sources, which was compiled by the company and verified by registered users.

Many theories exist to explain the persistent gap between male and female promotions, Jena said, including suggestions that women are promoted less often because they take time off from their careers during childbearing, that they choose specialties that offer fewer opportunities for promotion, or that they are less productive because, on average, they make different work-life choices than men.

It is also thought that the pre-existing shortage of senior women faculty members may make it hard for young women trainees to find mentors. These and other factors, the thinking goes, might make women less productive than men, and therefore, less likely to be promoted in a system that rewards .

Jena and colleagues wanted to see what the numbers said.

First, they found that there were some significant differences in productivity. Women averaged fewer total publications than men (on average, 11.6 publications for women vs. 24.8 publications for men) and fewer papers on which they were the first or last author (5.9 first or last authorships for women vs. 13.7 for men). They were also less likely to have NIH grants (6.8 vs. 10.3) or to have led large clinical trials (6.4 percent vs. 8.8 percent). But most of these differences stemmed from the fact that female faculty were younger, on average, than male faculty.

When the researchers looked at women and men with identical age, experience and research productivity, they found that women were nearly 13 percent less likely to be full professors than their male peers.

Answering the question of equal pay for equal work is challenging across professions, Jena noted, because it can be difficult to find big data sources with good measures of productivity. Since research productivity is the major currency of success in academic medicine, the number of papers, grants and clinical trials serve as an objective measure to compare the output of individuals of different sexes.

"What we see here is that women and men doing equal work are not being equally rewarded," Jena said. "If the goal is to achieve equity, or to give incentives for the best researchers to stay in academic medicine, we need to work on closing that gap."