But after statistical adjustment for such differences, a substantial, unexplained pay gap persisted, the researchers noted. The $3,600 difference in 1999 did not reach statistical significance, but the $16,819 difference in 2008 did.
"It may be that lifestyle factors are increasingly important to newer physicians," said Lo Sasso, whose wife is an ob/gyn. "It could be that women in particular want to have more of a lifestyle balance in their medical careers."
The results came as no surprise to Dr. Molly Cooke of the University of California San Francisco, who has watched salary-negotiation strategies play out over her 30-year career.
She also agreed with Lo Sasso's assessment that lifestyle issues, in general, are more important to women than to men who enter the medical profession.
"I think that there probably are a certain proportion of women making lifestyle choices at the expense of salary," Cooke said in an interview with MedPage Today. "I know that if you look at specialty choice by gender and ask men and women what is important to them as they think about their future specialty in medicine, men rank money higher than women. I think that plays out some in negotiations."
Physicians have more flexibility in their work style, she added. If a female physician wants to work a certain number of hours so she can spend more time at home with her children, opportunities exist today that were not available when Cooke entered the medical work force.
Another possible factor in the pay disparity is that women are more likely to be married to physicians or other professionals than men are. The woman may find herself disadvantaged in negotiations, particularly if the husband is the one being recruited. In such cases, the practice or recruiter might be "just finding a job" for the woman, said Cooke.
Female physicians also have a tendency to sell themselves short.
"I have talked with a lot of residents who are completing training and looking for their first job," said Cooke. "It's not all that uncommon for women to say, 'I just felt so lucky that UCSF offered me a job. I'm so lucky to get to be here.' I have to say, 'You're not lucky to be here; we're lucky to have you.' A lot of women just don't do that much negotiating."
"I know that's a stereotype, but like a lot of stereotypes, there's a certain amount of truth in it," she added.