We are all familiar with the fact that women are under-represented in positions of power. Women account for less than 5 percent of Fortune 500 CEOs, less than 15 percent of executive officers, less than 20 percent of full professors in the natural sciences, and only 6 percent of partners in venture capital firms. There have been zero female presidents of the United States.

This gender imbalance in high-level position has attracted the attention of scholars across disciplines for years. To date, the research has identified two main reasons for these gender differences at the top. First, women often face gender-based discrimination in the workplace. Women encounter greater challenges to their ideas and skepticism about their abilities at work, in part because people view women as less competent than men and less likely to be great leaders. When women attempt to engage in assertive behaviors, they often face criticism and backlash. For example, Yahoo CEO Marissa Mayer’s recent decision to take minimal maternity leave upon the arrival of her twins was met with much judgment, dismay, even outrage. Second, differences in men’s and women’s perceptions, decisions, and behaviors may affect their advancement—differences that are often driven by learned cultural norms or fear of backlash. For example, men are more likely than women to engage in dominant or aggressive behaviors, to initiate negotiations, and to self-select into competitive environments—behaviors likely to facilitate professional advancement.

These findings are clearly important, and they remind us of what the workforce looked like a few decades ago –lots of male faces and too few females ones. However, we’ve recently done research suggesting another important part to the story: men and women have fundamentally different preferences for achieving high-level positions in the workplace.

We collected data in nine studies from over 4,000 people from diverse populations, including executives in high-power positions, working adults who took surveys online, recent graduates of a top MBA program, and college students. Our results show that, at all of these stages of life, women have more life goals, and a lower proportion of their goals relate to achieving power at work. Women view high-level positions as equally attainable as men do, but less desirable. Though they associate professional advancement with the same positive outcomes as men do (such as respect, prestige, and money), women associate advancement with more negative outcomes (such as stress, time constraints, and tradeoffs). It is of course not for us to say if these preferences are wrong or right — they just are.

Consider this example. After thoughtful deliberation, a female mid-level manager we know decided to decline the prestigious promotion she had been offered. The position included privileges like leading a team of thirty talented people and having a strong say in the firm’s strategic decisions. The promotion would bring her more influence, money, power, and respect from her colleagues. She had no doubt she would excel in the job—it was not a lack of confidence that caused her to turn it down. Rather, in addition to the allure of the position, she also foresaw many downsides: more anxiety and stress as well as difficult tradeoffs in the way she would need to allocate her time to activities at work and outside of work. The higher-level position was likely to create conflicts with her other life goals, such as starting a family, maintaining her friendships, being a loving spouse, and staying fit. She turned down the promotion not because she could not do it, not because she did not want it, but because she wanted other things too.

In our MBA and executive classes, and during our site visits to companies in a wide range of industries, we have met many women like this one, women who have chosen not to advance in their professions, even when they were given opportunities to do so and had unshakable confidence in their abilities. Their preferences for achieving high-level positions in the workplace were different than those of their male counterparts.

Our recent research suggests that this difference in preferences between men and women is quite common. In one of our studies, for example, we showed some 630 recent graduates of a prestigious MBA program a ladder with rungs numbered 1 to 10. We asked them to imagine it represented the hierarchy of professional advancement in their current industry. Then we asked them to indicate three different positions on the ladder: (1) their current position in their industry, (2) their ideal position, and (3) the highest position they were capable of attaining. We did not find any differences between men and women in the current position they reported. And men and women reported similarly high levels for their highest attainable position. But women’s ideal position was lower.

We found the same pattern of results in studies using other populations, such as adults working across a wide range on industries as well as college students. For instance, in one study, we asked 500 people to imagine being promoted to a higher-level position in their current organization. The position, we told them, would substantially increase their level of power over others. Participants predicted the extent to which they would experience positive and negative outcomes if they decided to accept the promotion. The positive outcomes were satisfaction or happiness, opportunity, money, and status or influence; the negative ones were stress or anxiety, difficult trade-offs or sacrifice, time constraints, burden of responsibility, and conflict with other life goals. Participants also indicated how desirable the promotion would be to them and their likelihood of pursuing it.

What we found in that female participants expected the promotion to bring more negative outcomes as compared to male participants – but the same level of positive outcomes. What’s more, female participants viewed the potential promotion as less desirable than men did and reported being less likely than men to pursue it.

The explanation has to do with people’s core life goals. When we asked men and women to list their goals, women listed more. And a lower proportion of their goals related to achieving power at work. By definition, if you have more goals, you can’t allocate as much time and attention to any one of them (on average), including professional advancement.

You may wonder: Where do these preferences come from? They may be the result of biological sex differences, learned preferences that have developed in response to cultural norms and gender-based discrimination, or both factors. After all, people learn how to think and behave based on their experiences, observations, and interactions in the world. For example, research has found that women speak up less often than do men due to an acute awareness of the backlash that women frequently receive for voicing their opinions. Similarly, a woman may have a strong desire for power, but she may see how women in high-level positions act and are treated and decide that power is an undesirable goal for her.

Our findings provide a snapshot of our culture right now. If we ran these same studies fifty years ago (or fifty years from now), people’s answers would have been (and will be) different. Right now, it is likely that women have more goals in life because pursuing career and family goals simultaneously is a relatively new concept for women. These dual pursuits were far less common even fifty years ago. Although women are still interested in having strong relationships, marriage, and family, women also increasingly seek fulfilling careers. This is where society is now, and we are excited to see how things will shift in the future. We cannot say whether Sandberg’s advice to “lean in” is right, or Marissa Mayer’s decision to take an abbreviated maternity leave is optimal for her, for Yahoo, or for our culture, but our research adds a new piece to the puzzle. Even in societies that value gender equality today, the gender disparity at the top persists, in part, because women want different things—more things—than men.