Too few female CEOs? How we solve it.

There's just one woman among CEOs of the three dozen Fortune 500 companies based in Illinois. Why not more? The fact is that the selection process is still primarily driven by men.

This article originally appeared in Crain's Chicago Business.

This year's Crain's Chicago Business list of Chicago's most powerful women in business features one Fortune 500 CEO, Mary Dillon of Ulta Beauty, which just joined Fortune 500 this year when its revenue topped $5.8 billion. That's it—one out of the 37 Fortune 500 companies based in Illinois. The Fortune 500 overall hosts 5 percent female CEOs, down slightly from last year's "high" of 6.4 percent, after several departures. It's taken us 20 years to get this far. And clearly, none of these numbers are where they should be.

So why are the numbers still so low? We know it's not about education. Women have been graduating from the best colleges in equal numbers to men for more than a quarter-century. It's about what happens after women start working. They just don't stay in the corporate pipeline to the senior ranks at the same rate as their male peers.

Becoming CEO is a long-odds matching game. A company needs to have a pool of women at the highest levels, and at least one who is ready for the top spot at the same time the company is ready for a CEO transition. Given how few women are in the C-suite, and the even fewer in CEO-succession "line roles," these are low-probability events. Even when a woman gets the top spot, unlike typical market saturation models, the role usually goes back to a man after she steps down. We saw that happen with every female CEO transition over the past year: Avon, Campbell Soup, Ingredion, Mattel, Mondelez International, PepsiCo, etc.

Since most incumbent CEOs and board members are men, they still set the culture, tenor and tone for determining who is fit to succeed. And despite even the best of intentions, it's taking more time than anticipated to broaden the messaging and change the unspoken rules and expectations to bring more women into contention.

So let's get concrete—what has to happen to increase the pipeline so we can get more female CEOs? First, we need to make it easier for women to stay in the workforce during the child-rearing years. If you think about it, it's a strange world where a large determinant in whether a woman becomes a CEO contender is how her child care saga plays out in her 30s and 40s. I won't recount the statistics here about the challenges of finding affordable, convenient, high-quality child care. That said, it's rather telling that a large proportion of the C-suite women I've met had other family members (usually husbands or mothers) take over the at-home role amid their upward trajectories. I happen to know that CEOs Mary Dillon and Indra Nooyi of PepsiCo, for example, both fall in that category.

Second, we need to make the climb less draining. It really shouldn't require quite so much grit from women to get to the C-suite. In my role as dean at Kellogg, I had the opportunity to host a number of small-group dinners with senior women, women who were eager to build community with like-minded others. At these dinners, I heard many stories. The women who have made it to the senior ranks have withstood a lot. They have incredible fortitude and a strong desire to win, whether it be surviving numerous workplace #MeToo experiences that will never be publicly shared or blatant discrimination or only semi-implicit bias. It's truly stunning.

The reality for most women is that, if you're going to spend 10 hours or more a day away from your children and travel frequently, which is what the biggest jobs require, your work needs to be meaningful and fulfilling. Yet most CEOs and boards don't know just how trying the climate is for women and minorities at their organizations, especially as they get closer to the top. As I have advocated before, if a company is serious about diversity in the C-suite, whenever a high-potential female or other minority departs, board members should require an exit interview and detailed postmortem. The key point is to not delegate the task to HR. For true change, direct knowledge is needed and must be acted on at the highest levels.

Since 1998, we've moved from one female CEO in the Fortune 500 to 25. Over the next 20 years, we must do better. At the Kellogg School, we have been focusing on the key career "pivot points" that women must navigate in order to reduce the drop-off on the path to the C-suite. If we want to truly realize our potential as a society that espouses equal opportunity for all, we need to make it easier for more educated women to stay in the full-time workforce during the midcareer years. And we need more companies brave enough to rout out the barriers many women encounter as they reach for the biggest jobs.