They also attributed their optimism to "learning from scientists who are inventing cutting-edge tools to cure disease," speaking with government leaders around the world who "are being creative about prioritizing the health and well-being of people" and meeting people "who are imagining new ways to transform their communities."
Through the rest of the letter, Bill and Melinda further detail their optimism for global change by answering the following 10 "tough questions" they often get asked:
1. Why don't you give more in the United States?
2. What do you have to show for the billions you've spent on U.S. education?
3. Why don't you give money to fight climate change?
4. Are you imposing your values on other cultures?
5. Does saving kids' lives lead to overpopulation?
6. How are president Trump's policies affecting your foundation's work?
7. Why do you work with corporations?
8. Is it fair that you have so much influence?
9. What happens when the two of you disagree?
10. Why are you really giving your money away — what's in it for you?
In the foundation's 2017 annual letter addressed to Warren Buffett, Melinda Gates wrote that she believes "optimism is a huge asset."
"We can always use more of it. But optimism isn't a belief that things will automatically get better; it's a conviction that we can make things better," she wrote.
It's this very attribute that the billionaires say they admire about Buffett and apply in their personal and professional lives.
"We're trying to channel your empathy, add your optimism, mix in technology, apply strategy, and work with partners to save more lives," Melinda Gates wrote.
They hope people will "be just as optimistic as we are" after reading the responses to their 10 tough questions.
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