Melinda: When economists describe the conditions under which countries prosper, one of the factors they stress is “human capital,” which is another way of saying that the future depends on young people’s access to high-quality health and education services. Health and education are the twin engines of economic growth.

If sub-Saharan Africa commits to investing in its young people, the region could double its share of the global labor force by 2050, unlocking a better life for hundreds of millions of people.

Girls’ education, especially, is among the most powerful forces on the planet. Educated girls are healthier. They are wealthier. (If all girls received 12 years of high-quality education, women’s lifetime earnings would increase by as much as $30 trillion, which is bigger than the entire U.S. economy.) And their families benefit, too. The more education a woman has, the better equipped she is to raise healthy children. In fact, UNESCO estimates that if all women in low- and middle-income countries finished secondary school, child mortality in those countries would fall by about half.

Eoin Treacy's view

The central themes to this letter and the foundation generally are innovation can solve most of our problems and educating girls educates future families. That is a return on investment anyone can understand.