From early childhood, we each saw how our parents helped out in our local communities, and we were taught that anything is possible.

Unfortunately, factors outside of anyone’s control make it hard for some people to reach their potential: things like when they were born, who their parents are, where they grew up, whether they are a boy or a girl.

We wake up every day determined to use our resources to create a world where everyone has the opportunity to lead a healthy and productive life. Most importantly, we believe this: All lives have equal value. That’s why we made the decision to donate our wealth from Microsoft to help others.

The challenge when we started out was how to do that in a meaningful and high-impact way. We were drawn to things that sprang from our experience, so we began donating PCs to public libraries across the United States to give everyone a chance to use one. As we read and traveled more, we also became curious about inequalities further from home.

One day, we read a newspaper article about millions of children in poor countries who die from diseases, such as diarrhea and pneumonia, that were easily treated in wealthier countries. That blew our minds. As new parents it hit us especially hard. If there’s anything worse than the death of a child, we said to each other, then surely, it’s the preventable death of a child. We sent the article to Bill Sr. with a note:

Those eight words changed the rest of our lives.

We started consulting experts, learning from locals in the countries where we wanted to work, and researching disease and poverty more deeply. We tried to figure out how we might use our voices to raise the visibility of global health, and how our resources could start saving and transforming lives.

We also expanded our work in the United States from providing access to computers and the Internet to making sure that every student had an equal opportunity to learn, graduate, and succeed.

As our commitment to our work grew, we transferred $20 billion of Microsoft stock to our foundation, making it the largest of its kind in the world. We devoted more and more time to its work until we were both doing it full-time. And when our good friend Warren Buffett donated much of his fortune to our foundation, it allowed us to raise our ambitions about taking on the toughest, most important problems.

Our foundation has spent $53.8 billion since 2000, and we think that’s helped our partners make a difference. How do we know? We are committed to measuring progress so we can see what’s working and what isn’t. We’d like to leave you with one chart we find most hopeful.

It’s this. The number of children who die each year before their fifth birthday. It’s fallen by half since the year 2000. Millions more kids are surviving. That makes us optimistic.