In the business world, women leaders are still a minority. This statement comes as no surprise to most of us; what is surprising is that men outpace women in leadership roles across every sector in the world: corporate, nonprofit, government, education, medicine, military and religion.

During the past three decades, women have achieved parity with men in the number of both employees in the workforce and positions in middle management. Women now comprise 57 percent of the total U.S. job market and 52 percent of all management roles and professional occupations, such as physicians and attorneys. They represent a full 60 percent of bachelor’s degrees earned at U.S. universities and also outpace men in the total number of master’s and doctorate degrees.

At Fortune 500 companies, however, women hold only 19 percent of board seats and 15 percent of executive officer positions, and the number of female CEOs at these companies is a paltry four percent. Four percent of 500 companies equals 20 female CEOs, with male CEOs running the remaining 480 companies.

When you look at it from this perspective, women have a long way to go. The significance of these statistics and the implications on leadership are cause for both concern and discussion. What is causing this gap and keeping women from advancing to the top?

Barriers to Leadership

In my doctoral dissertation, I examined the barriers that hinder women’s career advancement, including emotional intelligence and gender culture, and how these differences impact leadership. The findings showed that the reasons for the gap between men and women are multifactorial and deep-seated and have existed for generations. Further, problematic beliefs and perceptions are held by both men and women. It’s these reasons that make the problem difficult to address.

There are four types of barriers to leadership for women: structural barriers, institutional mindsets, individual mindsets and lifestyle choices.

Structural barriers include lack of access to important informal networks, such as the golf course, sporting events or simple after-work drinks. Often, men assume that women don’t want to take part in these types of events, so they don’t invite them.

Golf has been the standard means of building client relationships for decades and still is today in many industries. Even though many women now play golf, this practice is still a predominantly male bastion. If golf is the default method of building client relationships at your organization, what are the implications if the best person for an account doesn’t play?

We must be more inclusive with our networks and social events. Men need to invite women, and women need to invite men. Chances are they’ll have fun too, and you never know what the outcome may be when diverse groups interact. It is the best way to fully leverage talent and remain competitive in your industry.

Institutional mindsets include various types of gender bias and stereotyping. For example, role incongruity occurs when someone holds beliefs or stereotypes about a group that are inconsistent with the behavior thought to be necessary to succeed in a specific role. In other words, there is a common belief that gender differences make women and men effective in different roles. Thus, women are less effective to the extent that the leader role is masculinized, and men are less effective when the role is feminized.

For example, a woman can be a very effective military leader, but her platoon may not support her, because she’s in a role considered to be incongruent with femininity. A similar problem exists with male nurses: A man can be an excellent nurse, but those he cares for may not receive him positively, because he’s in a role considered incongruent with his gender. Role congruity theory makes it difficult for men and women to succeed as leaders if their behaviors are not perceived to be congruent with their genders.

Furthermore, many people associate leadership behaviors with agentic behaviors, which are associated with stereotypical masculine traits such as assertiveness, aggression, competitiveness, dominance, independence and self-reliance. This association creates a conflict for women when they attain leadership positions, because they are expected to act like a leader (“male” traits) and like a woman (“female” traits). Thus, to be accepted as leaders, women often must walk a fine line between two opposing sets of expectations.

Individual mindsets are the thoughts and behaviors women might have that that hold them back. Data show that most women reach the director level and stay there, or self-select out of the workforce. The majority of women do not pursue vice president, president or C-level positions for a myriad of reasons, including socialization pressures, lack of confidence, risk aversion, valuing work-life balance or a desire to avoid politics.

It’s important to note that women often want different things than men do and are confronted with barriers that men do not have to face. As a result, many women have opted for the private sector, nonprofits or startup companies, where there are a significant number of female owners, leaders and employees. They can then avoid some of the barriers women face in large public companies, discovering less gender bias and stereotyping, more female mentors, more female role models and more leadership support to help women advance.

Lifestyle choices include work-life balance, family choices and breadwinner/caregiver priorities. These choices are not negative, but they are considered barriers, because they contribute to the leadership gender gap.

For example, if a woman is the primary breadwinner in a household, she’s usually the primary caregiver as well. On the other hand, if a man is the primary breadwinner, he is rarely the primary caregiver. This is an important distinction that families must carefully consider when discussing career aspirations. The more balance there is at home, the more balance there will be at work.

Solutions to Leadership Barriers

At any given point in a woman’s career, she is likely to experience one or more of these barriers. Sometimes the barrier is overt, and other times the barrier will be concealed behind another agenda. For example, a mother with a young child at home applies for a leadership assignment that requires more travel. She doesn’t receive the assignment and is told that another candidate is more qualified, which is false. The real reason is that the boss assumed that because she has a young child, she won’t want to travel or commit to the assignment. She is passed over as a result of gender stereotypes.

Overcoming Structural Barriers

We can help overcome structural barriers with mentors and sponsors, but it’s important to understand the difference between the two. A mentor is a person who helps guide and advise someone to grow in her current position. A sponsor is a person who serves as someone’s advocate to help her move toward her next position.

For women, a good strategy is to have male sponsors who are in decision-making positions of authority and can give them more credibility. These sponsors can include their boss, leaders in their department or leaders in other departments.

For example, let’s assume that you’d like the vice president of human resources to be your sponsor, but you don’t know him. One solution is to reach out to him directly and set up an introductory meeting. If you’re not comfortable with doing so, find someone who knows him and ask to be introduced or referred. Be clear on what you want from him and what you are seeking to accomplish.

Changing Institutional Mindsets

Institutional mindsets are the most significant barrier and are a major reason that we don’t see more women at the top levels of leadership. People make assumptions about women at work and as leaders based on their stereotypical roles in society. Often, women are limited in their advancement or, worse, never even given an opportunity because of bias.

Even more worrisome, much of the bias that people have toward women is unconscious. Research has found that it’s not the conscious or explicit bias that primarily causes barriers and misunderstandings and limits potential. Rather, it’s the unconscious or hidden biases that are really problematic.

These hidden, reflexive preferences shape our worldviews and can profoundly affect how welcoming and open a workplace is to different people and ideas. One solution is for women to proactively and consistently communicate their desires to advance, travel or take a new assignment. This type of communication will help put to rest any assumptions made about them.

Changing Individual Mindsets

One example of individual mindsets or limitations is office housework: getting the coffee, taking the notes, picking up the donuts, helping new hires, planning the holiday party and all the other behind-the-scenes work that helps a company run smoothly. Women frequently volunteer for office housework, which is time-consuming and often isn’t recognized. On the other hand, men tend to volunteer for activities that are more visible.

One solution is for women not to volunteer for these types of activities every time. While they are supportive and helpful, let other employees contribute, including men. If you are responsible for selecting people for these activities, assign tasks rather than asking for volunteers, so you ensure an even gender distribution.

Accommodating Lifestyle Choices

Lifestyle choices and work-life balance priorities are more valued now than in previous generations. The most recent data show that millennial men value work-life balance as much as women have for the past several decades. However, there are many companies who still adhere to rigid work hours, structure and policies.

One solution is to seek employers that value (and promote) work-life balance and offer flexible options. If no options are available, request that your company create new programs or policies. Companies are now more responsive to employee and corporate pressures, and chances are that your colleagues want the same things, too.

What Can Learning and Development Do?

It is essential for both men and women to be aware of these barriers and work together to minimize them. They are the underlying causes of the leadership gender gap that significantly impacts corporations’ diversity and inclusion. Leaders, human resources departments and trainers play a big role, because all employees are affected by leadership development practices. These practices include whom we are developing, how we are developing them, when we’re developing them, on what issues they’re being trained and how leadership styles are applied.

As a learning and development professional, you can influence leadership development at your organization. For example, you can collaborate with human resources to create training programs that develop leadership talent, develop application-based workshops and assessments, develop training reinforcement and metrics, and educate employees about the barriers discussed in this article. Only after these barriers are removed will women advance in large numbers to senior leadership positions. It’s the only way to achieve more diverse, inclusive and balanced leadership across global organizations.