Still today, in almost all societies around the world, women are less well-off than men. Women are still paid less than men; they are less represented in business, politics and decision-making. Their life chances remain overwhelmingly less promising than those of men.

This inequality hurts us all. The world would be 20% better off if women were paid the same as men. Delaying early marriage in the developing world by just a few years would add more than $500 billion to annual global…