FORTUNE – Last summer, Lynn Good became CEO of Duke Energy. Under her leadership, the $25 billion company experienced a 50% increase in profits. Formally the firm’s chief financial officer, Good spent the year navigating Duke Energy (DUK) through a difficult merger with Progress Energy.
Good is one of just a handful of women — in the world — who became CEO of a large company last year. While 332 of the 2,500 biggest publicly traded companies globally brought in a new executive officer, women filled just 10 of those positions, according to a new study from management consulting firm Strategy&, formerly Booz & Company. Despite droves of women entering higher education and the global work force, the number of women filling top executive roles hasn’t budged for some time. In the past 10 years, 84 women have taken over the top role at the world’s largest firms compared with 2,942 men, according to Strategy&.
Strategy&’s initial findings on gender imbalance in the C-suite may not be encouraging (or surprising), but its projection for the future is slightly brighter. Citing trends in women going on to higher education, the share of women in the workforce and shifting social norms, researchers claim as much as a third of the incoming CEO class will be made up of women by 2040.
So how do we get from 3% to 33% in 25 years? Assuming that the median age of 53 for a CEO stays relatively the same, the women entering the workforce today will be eligible for CEO status in their careers by Strategy&’s projected 2040. Since 1970, the number of women enrolling in colleges worldwide has grown nearly twice as fast as the number of men. In the U.S., roughly 40% of all MBA candidates were women in 2012 and today women make up about 40% of the global work force.
Ken Favaro, Strategy& senior partner and author of the study, described the disconnect we see between the growing percentage of women going into business and the stagnating percentage reaching the executive level as a “numbers game.” It takes time for women entering business today to get enough experience to become eligible for leadership roles within their firms, he explained.
The other reason for the delay is, perhaps, more nuanced.
“A lot of these companies were started at least 50 years ago when there were no women in the workforce, much less running companies,” Favaro said. “It takes a long time for work culture to change … It is a cultural drag, but it is a drag that will decline over time.”
Companies in the U.S. and Canada, where Favaro explained the culture is advancing at the fastest rate, have garnered the highest percentage of women CEOs for the past decade. Although that figure comes in at only about 3%, Japan’s total is much smaller as less than 1% of women took on the top executive role over the last 10 years.
Favaro and his colleagues are confident that more women will become CEOs with time, yet other Strategy& findings paint a bleak picture for the future. Female CEOs are more likely to be forced out of their jobs than men; during the past decade, 38% of women CEOs left involuntarily compared with just 27% of their male peers. Women are also more often hired externally, a finding Favaro explained could lead to weaker internal relationships within their firms. Outsider CEOs, in general, also tend to get hired more frequently when a company isn’t performing well, according to Favaro.
One such former female CEO that fits the researchers’ findings is Yahoo’s Carol Bartz. After building Autodesk into a successful company, Bartz was hired to in 2009 to bring Yahoo back to its heyday. Despite reducing costs, she failed to improve revenue growth just as Yahoo was losing the advertisement dollars game to Google and Facebook. In 2011, a Yahoo (YHOO) chairman fired Bartz — over the phone.
“These people f—ed me over,” Bartz told Fortune at the time of her dismissal.
Strategy&’s findings and Bartz’s story both support the theory of the glass cliff, which claims that women are more often promoted into leadership roles in times of crisis. The concept has come into focus recently as GM CEO Mary Barra deals with the fallout of a recall of millions of vehicles. As Fortune’s Allan Sloan recently pointed out, Barra became an icon of sorts when she became GM’s (GM) first female CEO this year, but now is forced to deal with problems that started well before her tenure.
If Barra weren’t a woman, perhaps we wouldn’t be seeing her name criticized so heavily in the media, Favaro said.
“When we first looked at the percentage of women CEOs coming in, I was shocked,” Favaro said. “When Mary Barra got promoted to GM, it was all over the place … And the reason we were reading about it so much was because [women become CEO] so infrequently. It definitely isn’t old hat.”