Are men and women different? While almost every executive I have ever met, anywhere in the world, says yes, most diversity policies are designed as if the answer were no.

Last week, the Global Head of Diversity of a leading professional services firm told me that she “didn’t want to be treated differently.” That, I answered, is why most professional services firms are still hovering well below the 20% female partner level. As long as men and women are treated exactly the same by organizations, most women will continue to be shut out of senior roles.

And yet for the past 30 years, managers have been taught to do just this: treat men and women exactly the same. That is considered the progressive thing to do. Any suggestion of difference was, and often still is, labelled a bias or a stereotype, especially by many women, eager to demonstrate that they are one of the guys, or the in-group. READ MORE: To Hold Women Back, Keep Treating Them Like Men | HBR.