Bill and Melinda Gates answer the 10 Toughest Questions they get asked:

Compare today to the way things were a decade or a century ago. The world is healthier and safer than ever. The number of children who die every year has been cut in half since 1990 and keeps going down. The number of mothers who die has also dropped dramatically. So has extreme poverty—declining by nearly half in just 20 years. More children are attending school. The list goes on and on.

But being an optimist isn’t about knowing that life used to be worse. It’s about knowing how life can get better. And that’s what really fuels our optimism. Although we see a lot of disease and poverty in our work—and many other big problems that need to be solved—we also see the best of humanity. We spend our time learning from scientists who are inventing cutting-edge tools to cure disease. We talk to dedicated government leaders who are being creative about prioritizing the health and well-being of people around the world. And we meet brave and brilliant individuals all over the world who are imagining new ways to transform their communities.