This story was co-published with The New York Times' The Upshot.

Few women are on the list of doctors paid the most money by drug and medical device companies last year, according to a ProPublica analysis of new data released by the federal government.

More than 90 percent of the 300 doctors who collected the most money for speaking and consulting are men, based on information from the new government database, called Open Payments. By comparison, men accounted for about 68 percent of active physicians in the United States in 2012, according to the Association of American Medical Colleges.

What we found adds to a growing body of evidence that male and female doctors are paid differently and may in fact practice medicine differently, though the reasons for the discrepancy are not completely clear. It's possible that men are more willing to accept payments from drug companies than women. It's possible that drug companies are more likely to make offers to male doctors. Or it's possible that male doctors are simply much more likely to be in the senior positions or medical specialties that appeal to drug companies.

But even in primary care fields, men dominated the list of the 300 highest-paid speakers and consultants in Open Payments. Of the 91 internists, just 12 percent were women. Nationally, women made up 34 percent of internists in 2010. There were five obstetrician-gynecologists on the list; all were men.

There are plenty of caveats regarding the new federal data. It covers only the last five months of 2013, and more than one-third of speaking and consulting payments are missing the names of those who received them. (The government redacted the names, citing data inconsistencies.)

That said, the broad finding is consistent with Dollars for Docs, ProPublica's online search tool that reflects payments made by 17 drug companies over four years. The overwhelming majority of large payments for speaking and consulting went to men. In an analysis we performed last year, 21 of the 22 doctors who earned more than $500,000 in speaking and consulting fees were men.

The federal data set covers all drug and device companies — more than 1,000 in all.

The data doesn't explain why the gender disparity exists. While current medical school classes are close to evenly split between male and female students (men still have a slight edge), many subspecialties are still dominated by men, as are the leadership ranks of medicine.

"I don't perceive any gender bias from my colleagues, the people I work with," said Alison Tendler, a South Dakota ophthalmologist who was among the top-paid women, primarily because she serves as the TV advertising spokeswoman for the eye drug Restasis, made by Allergan.

"I do feel that we can be potentially overlooked from an industry standpoint for being leaders and innovators in our likely professions,"Tendler said. "I'm not sure if they perceive us as not as assertive. I'm not sure why."

Tendler said she sees a gender divide, although not in her interactions with Allergen. "In general, you have to raise your hand a little higher," she said.

Some of the other female doctors on the top-paid list are well-known academics and researchers. Nesli Basgoz, a leader at Massachusetts General Hospital, is on the board of directors of the drugmaker Actavis and was on the board of Forest Labs, which Actavis acquired this year. Alessia Fornoni is the director of the Peggy and Harold Katz Family Drug Discovery Center at the University of Miami Miller School of Medicine.

Basgoz could not be reached for comment. The Miller School of Medicine declined to comment on Fornoni's behalf.

What's clear from research is that women in medicine earn less than men. A study last year in JAMA Internal Medicine found that the median earnings of male physicians exceeded those of female ones by more than $56,000 between 2006 and 2010, a bigger gap than in prior years, even after factoring in inflation. The data was adjusted for hours worked and for years of experience, but not for physician specialty. Some specialties, like dermatology or orthopedic surgery, pay better than general practice.

A 2011 report in the journal Health Affairs also found a gender disparity among doctors who recently completed their residency training programs. It persisted even after taking into account doctors' choice of specialty.

Gender differences were once again on display in data released earlier this year on Medicare's payments to physicians. An analysis by the website Nerd Wallet found that men, on average, were paid 88 percent more than women in Medicare reimbursements in 2012. Men saw more Medicare patients, performed more services per patient, and were paid more money per patient. This gap persisted within specialties in which women have a larger presence, including obstetrics and gynecology.

Roberta Gebhard, national secretary of the American Medical Women's Association and chairwoman of its gender equity task force, said the dearth of women among the industry's top-paid list was "not a surprise."

"In my experience, women are less likely to be in the specialty that's going to be tapped," she said. "They're less likely to be asked if they're in that specialty. And then if they are asked, they are less likely to accept" payments from drug and device makers. Gebhard said her female colleagues don't want to be unduly influenced by such relationships.

Anthony T. Lo Sasso, a professor of public health at the University of Illinois at Chicago, was the lead author on the 2011 Health Affairs article. He said women have tended to work in primary care fields, such as internal medicine, family medicine, pediatrics and obstetrics-gynecology, which provide fewer opportunities for consulting and speaking work.

In 2010, for example, women made up just 4 percent of orthopedic surgeons in the United States. (Thirty-nine male orthopedic surgeons — and no women — were among the 300 top speakers and consultants.)

"The notion that women physicians may be willing to trade off some income for greater flexibility" to improve the work-life balance may be a consideration, he said. Consulting and speaking engagements take even more time after work hours. "If they're willing to forgo some salary in order to get some predictability and to balance work and nonwork life, it wouldn't necessarily be surprising to see them not take up these additional consulting gigs," he said.

Anupam B. Jena, a professor of medicine at Harvard Medical School and a doctor at Massachusetts General Hospital, said the proliferation of data on gender disparities among physicians was ripe for further study. Jena, an author of the 2013 JAMA Internal Medicine report, suggested that physicians' ages and specialization would reduce the extent of the disparity in the Open Payments data, but may not eliminate it entirely.

"I wouldn't be surprised to see that even when you adjust for all these things, you still see more payments going to men than to women," he said.

Check Dollars for Docs to see whether your doctor has received payments from the 17 companies we track. Email us at [email protected] and tell us what you find.