Over the past five years, LeanIn.org and McKinsey & Company have taken a yearly look at the status of women in corporate America. In that time, we have analyzed data from close to 600 companies and more than 250,000 employees. And every year, we have found that women are underrepresented at each level of the pipeline, from entry-level jobs all the way to the corner office. This is especially true for senior-level positions, and that's thanks to an unseen and little understood problem blocking women's path to leadership: the broken rung. The broken rung is a dynamic that occurs at the beginning of the pipeline — at the first step up from entry-level to manager. At this critical juncture, we see a significant gender disparity in promotion and hiring rates. For every 100 men that are promoted and hired to manager, only 72 women are promoted and hired. This disparity means that men end up holding 62% of manager-level positions, while women hold only 38%. This early inequality has a lasting impact on the pipeline. At every subsequent level, the number of men increases, while the number of women decreases. Even though women make up 48% of entry-level employees, by the time we get to the C-suite, women hold only 21% of those jobs. In contrast, while men hold just over half of entry-level jobs, they end up holding a whopping 78% of the C-suite jobs. Because of the broken rung, over the next five years, about one million women will get stuck at the entry level while many of their male colleagues will move up a rung. Why would women fall behind so early? The broken rung indicates that gender bias may play a role in decisions made about which employees are seen as ready for their first shot at leadership. Research shows that women often have to provide more evidence of their competence to be seen as equally skilled as their male counterparts. In other words, compared to men, women are held to higher standards and have to do more to prove themselves than men. In this case, at more junior levels when employees don't have much of a track record, junior-level men may be getting promoted to manager based on their potential, while junior-level women may have to achieve more before they get their shot. Other factors may be at play here, too. But the end result is that too many women are getting stuck at entry level. When the underrepresentation of women is the norm, gender inequality becomes like background noise — so ever-present it doesn't even register. This is certainly the case with the broken rung. While it is a significant problem, it remains an unseen barrier, even by those who are most impacted by it. When asked to identify the biggest challenges to getting equal numbers of men and women into management, only 19% of human resource leaders (men and women), 19% of women employees and 7% of men employees say it's because "women are less likely to be promoted to first-level manager roles." Moreover, employees appear not to even notice the disparity to begin with. When just one in three managers in their company is a woman, an eye-popping 62% of men and 54% of women think women are well-represented at first-level management. More Perspectives on Management & Leadership LGBT workers should be protected. Let's hope the Supreme Court agrees 4 signs a company is a good employer for womenAmerica is facing a leadership crisis. It's on us to fix it Perhaps because they don't see the problem, many have a misperception that progress is going to happen over the next decade. In fact, over half of HR leaders and employees think their company will reach gender parity in leadership over the next 10 years. However, the reality is this: If current trends continue, it's unlikely we will reach gender parity in corporate America — ever. To fix the broken rung, companies need to clearly see the problem at hand. This requires quantifying it. While many companies track the overall representation of men and women by level, fewer track promotion and hiring rates by gender, race and other characteristics. And even fewer analyze the data to track these dynamics over time to pinpoint any disparities. It's only when companies truly identify and understand what's getting in the way of fairness that they can then design programs and initiatives that tackle the problem head-on. It turns out that fairness doesn't just happen. Companies must work to achieve it.