Women hold nearly 52 percent of all professional-level jobs, but 75 percent of executive- and senior-level officials are men. Meanwhile, only 4.6 percent of CEOs at S&P 500 companies are female. Researchers have chalked this disparity up to a number of factors, a large one being that women presumably don’t want to sacrifice work-life balance or a family for a career. But according to a new analysis conducted by Sheryl Sandberg’s nonprofit LeanIn.Org, many women simply aren’t interested in becoming a top boss—and they provide a variety of reasons for their decision.

LeanIn.Org teamed up with management consulting firm McKinsey & Company to conduct the “Women in the Workplace 2016” report. They collected 132 companies' pipeline data and surveyed more than 34,000 employees about their career opportunities and goals.

Many of the findings are similar to insights culled from other workplace studies (for example, women do in fact ask for raises, but are less likely to receive them). But the Women in the Workplace study also revealed that only 40 percent of senior female managers said they wanted a top executive job, in contrast with 56 percent of men.

When asked why they don't want to be a top executive, 42 percent of both women and men said "I wouldn’t be able to balance family and work commitments." Their opinions differed, however, when imagining the experience of being at the top. A third of women, compared to a fifth of men, said they didn't want the pressure that comes with a top-level job. And only 43 percent of women, compared to 51 percent of men, believed becoming a top executive would "significantly improve their ability to impact the business." According to the report, this may be because "women may not think their ideas and contributions carry the same weight as men’s."

Even if a woman does want to become a CEO, she faces a much more difficult climb than her male co-workers—partly because her chances for advancement are thwarted early on in her career. The survey found that for every 100 women promoted to their first managerial position, 130 men are promoted, making it harder for women to progress into leadership positions. In general, fewer women are also hired from the outside than men, and when they do get their feet in the door they receive “less access to the people, input, and opportunities that accelerate careers,” the report states. It's no surprise, then, that the report also shows that early-level female employees are nearly three times as likely as men to think their gender will hinder them, career-wise.

"This report is a reminder, yet again, of how much is left to do," Sandberg concluded in an editorial for The Wall Street Journal. In order to close these gaps, companies need to advocate for gender diversity, provide gender-bias training for managers, and address gender stereotypes head-on.

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