If you can't go to secondary school, the boys get to go and the girls don't, you're locked into a cycle of poverty, because you don't have a chance.

In places like India with smartphones, there's an app now for women if they're in a violent situation, they can press one button. They've given their cell-phone number to five trusted friends, and right away their GPS location goes out: "Here I am."

If you don't have an effective teacher in front of the classroom, you won't change the trajectory for students.

Despite the debunking, you have a small group in the last five years that hasn't wanted to vaccinate their children, for instance, for measles. Then, all of sudden, we got an outbreak of measles and kids were starting to die from measles.

We have to look at it country by country. In places like the developing world where, as you say, in Mumbai, it's about five hours' gap between what a woman does and a man does. You have to start by recognizing the problem and talking about it, trying to change those roles.

If you want to lift up an economy in Africa, you basically start with the women.

Contraceptives unlock one of the most dormant, but potentially powerful assets in development: women as decision-makers. When women have the power to make choices about their families, they tend to decide precisely what demographers, economists, and development experts recommend. They invest in the long-term human capital of their families.