For a long time, like many elite academic fields, the world of PhD economists was almost exclusively a boys club -- back in 1970, only 5 percent graduated by U.S. universities were female U.S. citizens. That gradually started changing, though, and the proportion reached a high of 16 percent in the mid-1990s.

But progress isn't necessarily a linear upward trend toward gender parity, as Wendy Stock of the University of Montana and John Siegfried of Vanderbilt find in a study presented at the American Economics Association conference over the weekend. The proportion of female U.S. citizens landing economics degrees is now back around 11 percent. And while the share of female non-U.S. citizens continued to rise, the combined percentage has stagnated at about a third of total graduates.

Why the retrenchment? It may have to do with another phenomenon the researchers noticed in a survey of graduates over the last 15 years:
When examining demographic and graduate school factors associated with salary growth during the early career years, we found that marriage was significantly associated with salary growth, with those who were married at the time they earned their degree experiencing roughly 15 percent higher salary growth over the first five years of their careers. For males, getting married within the first five years after graduation was associated with a 25 percent salary growth premium relative to other males. For females, however, getting married was associated with a 23 percent salary growth penalty relative to other females, perhaps reflecting compromises incurred in a two-career job search.

"Compromises incurred in a two-career job search." "Compromise" suggests a level of equality, but the data suggests that women are more often the ones who sacrifice for their husbands' careers. That could mean that women tend to be the ones who move so that their partners can take better jobs. But it also likely correlates with the fact that marriage tends to come with kids, and the burden of caring for them falls more heavily on women -- the Pew Research Center last month found a big gender gap in the proportion of people who take time off to care for family members, and the negative career impact on those who do.

There might not be a direct causal relationship between those two findings, but both are bad news for women in the economics field (as well as statistics and math, where the trend is similar). And even though the pool of people we're talking about is small, at only about 1,000 per year, it's a pretty influential group -- they shape the rules that govern the global economy, and having women represented is important. Having Janet Yellen chair the Fed is one thing. Allowing other women to follow her lead is another.