McKinsey & Co. recently released "Women in the Workplace," a comprehensive study of the state of women in corporate America today. The study, which covers nearly 30,000 professionals from 118 companies, details a range of industries including finance, health care, media, technology, and retail.

The conclusions are important because they help illuminate why we have so few women in leadership. If we can understand the problem, maybe we can come up with solutions.

Here are some key points:

Women are not properly represented.

Many people assume this is because women are leaving traditional corporate life at higher rates than men, or because of the difficulties women face in balancing work and family. But the issue is more complex. The findings show that women face greater barriers to advancement and steeper paths to senior leadership. The rate of progress is so slow that it will take 25 years to reach gender parity at the senior VP level and more than 100 years at the C-suite level.

Women are more loyal than men.

Again contrary to assumptions, women on average are leaving their organizations at the same or lower rates then men. Women in leadership, in particular, are more likely than men to stay with their company, and women in C-suite positions are about twice as likely to stay.

Women are less likely to advance -- but not because of a lack of talent.

If women were advancing at similar rates to men, we'd expect to see the same share of women from one level to the next. However, that
's not the case. Women make up about 45 percent of those entering the professional workforce. At the senior management level, that percentage drops to 37 percent, and at the C-suite level to 17 percent. This suggests women face greater barriers to advancement at every level.

Women face obstacles to senior leadership.

In addition to the lower odds of reaching senior leadership, fewer women hold the roles that lead to C-suite positions. Most women who reach the VP level hold staff roles in support functions like HR and IT, while men are more likely to be in mission-critical line roles with greater potential for promotion to senior leadership. And, in a Catch-22, the women who are in line roles have less likelihood of reaching senior levels than those in support areas.

Women face an erosion of ambition -- and it doesn't seem to be connected to children.

Entry- and midlevel women and men share similar aspirations for promotion, but senior-level women are less interested in advancing than senior-level men. While women's and men's appetites for senior leadership differ, they share concerns about stress and balancing work and family. However, women of all ages, with and without children, are more likely to cite "stress/pressure" as a top issue. Men say balancing work and family is their main concern, and parents of both genders are more likely to say they want to be promoted and become a top executive. These findings point to another possible explanation: Women experience a disproportional amount of stress on the path to leadership.

Women face an uneven playing field.

Women are almost four times more likely than men to think they have fewer opportunities for advancement because of their gender, and twice as likely to think their gender will make advancement harder to achieve. Women are much more likely than men to say they have missed out 
on an assignment or advancement, and that they are less often consulted on important decisions, because of their gender.

Gender diversity is not seen as a priority.

While an overwhelming majority of companies report that gender diversity is 
a top CEO priority, fewer than half of all workers believe that is the case. Only a third view it as a top priority for their direct manager. If you separate out women workers, those numbers are even lower.

Women and men have different networks.

Women and men agree that networking and "sponsorship" are important to success, but they experience those things differently.  Although women's and men's networks are similar in size, their composition is different, with more men in men's networks. Since men are more likely to hold leadership positions, women may have significantly less access to senior-level people who can help them advance. And fewer women report help from such people in advancing.

Changing the structure and culture of work to remove women's barriers to advancement and create a more equitable environment will require a wide-ranging long-term effort, but it should be a critical concern for companies that want to perform at the highest levels.

We have insight into the disturbing reasons we don't have more women leaders. Now it's time to work on creating the solutions.