Much has been written about the lack of diversity in leadership positions in organizations across the globe, despite the large advancements women and nonwhites have made in the workplace. Only 19 Fortune 500 firms are led by people of color, and only 21 of these companies are led by women, according to recent data. And almost 75% of Fortune 500 boards are mainly comprised of white men.

In light of this data, you might expect that in organizations where women and minorities are at the top, they’ll try to help others like them climb the organizational ladder. Yet, this popular belief is not supported by data. In fact, research suggests, it is women and nonwhites themselves who often impede the advancement of their own peers. They do not advocate for them when positions come open or there is an opportunity for a promotion, and they do not provide the mentorship and support that everybody needs to navigate their careers successfully.

Scholars from a wide range of disciplines – from management to psychology and economics – have examined why this is the case.

One explanation is that both men and women are more likely to prefer to be led by a man than by a woman. A Gallup survey found that 33 percent of Americans reported preferring a male boss, while only 20 percent stating a preference for a female boss, in a new job; 46 percent said they didn’t have a preference. In addition, the longer women are in the workforce, the less likely they are to want a female boss. Laurie Rudman, a psychologist at Rutgers University, explains these preferences using the psychological concept of “system justification,” or the tendency for long-oppressed groups, struggling to make sense of an unfair world, internalize negative stereotypes. In the United States, as in many other countries, women don’t have the same status that men do. So when we ask ourselves whom we want to work for, we turn to the historical default choice: a man. Seeing few women leading organizations or managing people, we come to the faulty conclusion that female leadership is somehow an unnatural state of affairs.

Another explanation is that women and nonwhites do not support qualified candidates like them as potential high-prestige workgroup peers. For instance, Michelle Duguid of Cornell University finds that when a woman is the only woman of a high-status work group, she fears that she will not be seen as a valued group member and thus shows a preference for a man over a similarly qualified woman as a potential group member.

In one experiment, Duguid found that solo females felt more threatened by candidates of the same gender who had either higher or lower qualifications than they did. These women experienced three types of threat. First, they worried that female candidates with higher qualifications might end up being more qualified and competent than they are, thus setting up a competition in a context where only a few women are generally accepted. Second, women were also concerned about bringing in another woman with lower qualifications, who might reinforce negative stereotypes about women and impact others’ impressions of them. Finally, female tokens in high-prestige work groups were concerned about appearing biased toward other women. Ethnic minorities tend to share these three concerns. Because of them, women and ethnic minorities alike may fail to advocate for their peers.

There may be another reason why women and nonwhites may be reluctant to advocate for or support those like themselves. Specifically, ethnic minorities and women leaders are penalized when they engage in diversity-valuing behaviors—namely, hiring and promotion behaviors that promote greater demographic balance in organizations, according to new research by David Hekman of the University of Colorado and his colleagues.

The team of researchers identified this explanation in a study of 362 executives working in the United States. Almost 14% of the executives in this sample were nonwhite and about 31% of them were female. The executives were rated by both their bosses and peers on their performance as well as their diversity-valuing behavior. Analyses revealed that diversity-valuing behavior was negatively related to performance ratings only for nonwhite leaders and female leaders—those who had already broken through the glass ceiling. To advance their own careers, these results suggest, minorities and women are forced to avoid behaviors that others might perceive as promoting greater representation of people like them. Engaging in such behaviors, the researchers suggested, triggers a common, unfortunate stereotype of women and nonwhites being less competent than men and whites.

One common diversity-valuing behavior is to advocate for women and minority candidates. In a second experiment, the researchers asked 307 participants to read about a fictitious hiring manager who was choosing between two candidates for a vacant senior vice president position. Both candidates were equally qualified, but one belonged to a low-status demographic group (female or nonwhite), and the other was a white man. Participants also saw a photo of the hiring manager that revealed the person’s race and gender. The researchers varied whether or not the hiring manager engaged in diversity-valuing behavior. They did so by describing the hiring manager as not advocating for diversity and choosing the white make candidate (no diversity-valuing behavior condition) or as publicly advocating for diversity and choosing the demographically low-status candidate (diversity-valuing behavior condition). Next, the participants completed a survey where they rated the manager on competence and performance. The results were consistent with the researchers’ field evidence: participants—including women and nonwhites—rated female and minority leaders who advocated for candidates demographically similar to them more negatively.

We can easily find examples of this type of backlash in the real world. In the fall of 2016, Madeleine Albright and Gloria Steinem garnered criticism for advising young women to support presidential candidate Hillary Clinton. Likewise, Rosalind Brewer, an African American woman and Sam’s Club CEO, was called racist by the media for advocating for diversity. Women and minorities are often scrutinized when they try to increase diversity by favoring those like them, in a way that white men are not.

Over the last decades, many organizations have worked to increase racial and gender balance. The research I’ve discussed suggests a harsh reality that create barriers to the fair evaluation of women and minorities who are seeking access to the same opportunities as members of high-status groups. Leaders need to take steps to ensure that women and nonwhites are not penalized for their efforts to improve diversity in their organizations.