The number that explains the most about women at work is not the pay gap. It is a promotion gap that shows up on the very first step of the ladder. Researchers who study large companies call it the broken rung. For every 100 men who get promoted from an entry-level job into their first management role, only about 87 women make the same jump. That gap has narrowed over the years, from somewhere near 72 women not long ago, but it has not closed. Because it sits at the bottom of the ladder, it quietly shapes everything above it. Fix the number here and the entire structure starts to change. Ignore it, and every level higher simply inherits the same shortage.
The reason this one step matters so much comes down to plain math. If fewer women become managers in the first place, then fewer women sit in the pool for the next promotion, and the one after that. The gap does not stay the same size as you climb. It compounds, the way a small difference in interest compounds over decades. Each promotion above depends on the pool of people created below it. Starve that pool early and the whole ladder runs short near the top. You cannot fix the top by only recruiting at the top. The shortage was built one rung down.
People often assume the problem is women stepping back or leaving to raise families. The data tells a different story. Women are asking for promotions and changing jobs at rates close to men. The break is not in ambition, it is in who gets picked for that first management title. When companies actually track the numbers, they usually find they promote men on potential and women on proof. That single difference in judgment does most of the damage. The bias is quiet, but the result on the org chart is not.
Look closely at how those first promotions get made and a pattern shows up. A man is often moved up because a manager can imagine him growing into the role. A woman is more often asked to have already done the job before she is handed the title. One person is rewarded for promise, the other is asked for a track record. Neither manager thinks they are being unfair, and that is what makes it stubborn. It hides inside ordinary decisions that feel reasonable in the moment. Add up enough reasonable-sounding moments and you get a clear pattern. No single call looks wrong, yet the totals always lean one way.
The broken rung is not the same height for everyone. Women of color face the steepest version of it. For that group, the number of first promotions per 100 men drops well below the overall figure, into the low 70s in many studies. That means the pipeline problem is even sharper for Black and Latina women, who are underrepresented at every level that follows. When the first step is the hardest, the distance to the top only grows. The gap you can measure early predicts the gap you see later. The earliest step turns out to be the loudest signal of all.
Most companies miss this because they watch the wrong number. They count how many women they hire and how many sit in senior roles, and they set goals for both. The middle, where the first promotion happens, goes unwatched. Hiring more women at the entry level does nothing if those women stall at the first rung. And celebrating a few women at the top hides how few are moving up behind them. The fix starts with looking at the step nobody was measuring. You cannot manage a gap you have never bothered to track.
The companies that have narrowed the gap did a few plain things. They tracked promotion rates by gender at every level, not just headcount. They wrote down clear standards for what earns that first management job, so decisions rest on the same bar for everyone. They trained the managers who make those calls to notice when they reward potential in one person and demand proof from another. None of it is complicated. It is just measured, and what gets measured tends to get managed. Attention by itself starts to move the number.
The broken rung is a useful idea because it points to a fixable spot. It is not a vague sense that something is off at the top. It is a specific step, with a specific number, that a company can watch and change. Close the gap on the first promotion and the effect travels all the way up over time. Ignore it, and no amount of hiring or headline promotions will move the real picture. The first rung is where the ladder is actually broken. That is where any honest repair has to start.
