I am a little obsessed with fertilizer. I mean I'm fascinated with its role, not with using it. I go to meetings where it's a serious topic of conversation. I read books about its benefits and the problems with overusing it. It's the kind of topic I have to remind myself not to talk about too much at cocktail parties, since most people don't find it as interesting as I do.

But like anyone with a mild obsession, I think mine is entirely justified. Two out of every five people on Earth today owe their lives to the higher crop outputs that fertilizer has made possible. It helped fuel the Green Revolution, an explosion of agricultural productivity that lifted hundreds of millions of people around the world out of poverty.

These days I get to spend a lot of time trying to advance innovation that improves people's lives in the same way that fertilizer did. Let me reiterate this: A full 40 percent of Earth's population is alive today because, in 1909, a German chemist named Fritz Haber figured out how to make synthetic ammonia. Another example: Polio cases are down more than 99 percent in the past 25 years, not because the disease is going away on its own but because Albert Sabin and Jonas Salk invented polio vaccines and the world rolled out a massive effort to deliver them.

Thanks to inventions like these, life has steadily gotten better. It can be easy to conclude otherwise—as I write this essay, more than 100,000 people have died in a civil war in Syria, and big problems like climate change are bearing down on us with no simple solution in sight. But if you take the long view, by almost any measure of progress we are living in history's greatest era. Wars are becoming less frequent. Life expectancy has more than doubled in the past century. More children than ever are going to primary school. The world is better than it has ever been.

Dan Winters

But it is still not as good as we wish. If we want to accelerate progress, we need to actively pursue the same kind of breakthroughs achieved by Haber, Sabin, and Salk. It's a simple fact: Innovation makes the world better—and more innovation equals faster progress. That belief drives the work my wife, Melinda, and I are doing through our foundation.

We went on a Safari to see wild animals but ended up getting our first sustained look at extreme poverty. We were shocked.

Of course, not all innovation is the same. We want to give our wealth back to society in a way that has the most impact, and so we look for opportunities to invest for the largest returns. That means tackling the world's biggest problems and funding the most likely solutions. That's an even greater challenge than it sounds. I don't have a magic formula for prioritizing the world's problems. You could make a good case for poverty, disease, hunger, war, poor education, bad governance, political instability, weak trade, or mistreatment of women. Melinda and I have focused on poverty and disease globally, and on education in the US. We picked those issues by starting with an idea we learned from our parents: Everyone's life has equal value. If you begin with that premise, you quickly see where the world acts as though some lives aren't worth as much as others. That's where you can make the greatest difference, where every dollar you spend is liable to have the greatest impact.

I have known since my early thirties that I was going to give my wealth back to society. The success of Microsoft provided me with an enormous fortune, and I felt responsible for using it in a thoughtful way. I had read a lot about how governments underinvest in basic scientific research. I thought, that's a big mistake. If we don't give scientists the room to deepen our fundamental understanding of the world, we won't provide a basis for the next generation of innovations. I figured, therefore, that I could help the most by creating an institute where the best minds would come to do research.

Bill and Melinda Gates in Kenya's Kichwa Tembo Wilderness Reserve, 1993.

Courtesy of the Gates Family

There's no single lightbulb moment when I changed my mind about that, but I tend to trace it back to a trip Melinda and I took to Africa in 1993. We went on a safari to see wild animals but ended up getting our first sustained look at extreme poverty. I remember peering out a car window at a long line of women walking down the road with big jerricans of water on their heads. How far away do these women live? we wondered. Who's watching their children while they're away?

That was the beginning of our education in the problems of the world's poorest people. In 1996 my father sent us a New York Times article about the million children who were dying every year from rotavirus, a disease that doesn't kill kids in rich countries. A friend gave me a copy of a World Development Report from the World Bank that spelled out in detail the problems with childhood diseases.

Melinda and I were shocked that more wasn't being done. Although rich-world governments were quietly giving aid, few foundations were doing much. Corporations weren't working on vaccines or drugs for diseases that affected primarily the poor. Newspapers didn't write a lot about these children's deaths.

This realization led me to rethink some of my assumptions about how the world improves. I am a devout fan of capitalism. It is the best system ever devised for making self-interest serve the wider interest. This system is responsible for many of the great advances that have improved the lives of billions—from airplanes to air-conditioning to computers.

But capitalism alone can't address the needs of the very poor. This means market-driven innovation can actually widen the gap between rich and poor. I saw firsthand just how wide that gap was when I visited a slum in Durban, South Africa, in 2009. Seeing the open-pit latrine there was a humbling reminder of just how much I take modern plumbing for granted. Meanwhile, 2.5 billion people worldwide don't have access to proper sanitation, a problem that contributes to the deaths of 1.5 million children a year.

Governments don't do enough to drive innovation either. Although aid from the rich world saves a lot of lives, governments habitually underinvest in research and development, especially for the poor. For one thing, they're averse to risk, given the eagerness of political opponents to exploit failures, so they have a hard time giving money to a bunch of innovators with the knowledge that many of them will fail.

By the late 1990s, I had dropped the idea of starting an institute for basic research. Instead I began seeking out other areas where business and government underinvest. Together Melinda and I found a few areas that cried out for philanthropy—in particular for what I have called catalytic philanthropy.

I have been sharing my idea of catalytic philanthropy for a while now. It works a lot like the private markets: You invest for big returns. But there's a big difference. In philanthropy, the investor doesn't need to get any of the benefit. We take a double-pronged approach: (1) Narrow the gap so that advances for the rich world reach the poor world faster, and (2) turn more of the world's IQ toward devising solutions to problems that only people in the poor world face. Of course, this comes with its own challenges. You're working in a global economy worth tens of trillions of dollars, so any philanthropic effort is relatively small. If you want to have a big impact, you need a leverage point—a way to put in a dollar of funding or an hour of effort and benefit society by a hundred or a thousand times as much.

One way you can find that leverage point is to look for a problem that markets and governments aren't paying much attention to. That's what Melinda and I did when we saw how little notice global health got in the mid-1990s. Children were dying of measles for lack of a vaccine that cost less than 25 cents, which meant there was a big opportunity to save a lot of lives relatively cheaply. The same was true of malaria. When we made our first big grant for malaria research, it nearly doubled the amount of money spent on the disease worldwide—not because our grant was so big, but because malaria research was so underfunded.

But you don't necessarily need to find a problem that's been missed. You can also discover a strategy that has been overlooked. Take our foundation's work in education. Government spends huge sums on schools. The state of California alone budgets roughly $68 billion annually for K-12, more than 100 times what our foundation spends in the entire United States. How could we have an impact on an area where the government spends so much?

We looked for a new approach. To me one of the great tragedies of our education system is that teachers get so little help identifying and learning from those who are most effective. As we talked with instructors about what they needed, it became clear that a smart application of technology could make a big difference. Teachers should be able to watch videos of the best educators in action. And if they want, they should be able to record themselves in the classroom and then review the video with a coach. This was an approach that others had missed. So now we're working with teachers and several school districts around the country to set up systems that give teachers the feedback and support they deserve.

The goal in much of what we do is to provide seed funding for various ideas. Some will fail. We fill a function that government cannot—making a lot of risky bets with the expectation that at least a few of them will succeed. At that point, governments and other backers can help scale up the successful ones, a much more comfortable role for them.

We work to draw in not just governments but also businesses, because that's where most innovation comes from. I've heard some people describe the economy of the future as "post-corporatist and post-capitalist"—one in which large corporations crumble and all innovation happens from the bottom up. What nonsense. People who say things like that never have a convincing explanation for who will make drugs or low-cost carbon-free energy. Catalytic philanthropy doesn't replace businesses. It helps more of their innovations benefit the poor.

Look at what happened to agriculture in the 20th century. For decades, scientists worked to develop hardier crops. But those advances mostly benefited the rich world, leaving the poor behind. Then in the middle of the century, the Rockefeller and Ford foundations stepped in. They funded Norman Borlaug's research on new strains of high-yielding wheat, which sparked the Green Revolution. (As Borlaug said, fertilizer was the fuel that powered the forward thrust of the Green Revolution, but these new crops were the catalysts that sparked it.) No private company had any interest in funding Borlaug. There was no profit in it. But today all the people who have escaped poverty represent a huge market opportunity—and now companies are flocking to serve them.

Or take a more recent example: the advent of Big Data. It's indisputable that the availability of massive amounts of information will revolutionize US health care, manufac­turing, retail, and more. But it can also benefit the poorest 2 billion. Right now researchers are using satellite images to study soil health and help poor farmers plan their harvests more efficiently. We need a lot more of this kind of innovation. Otherwise, Big Data will be a big wasted opportunity to reduce inequity.

People often ask me, "What can I do? How can I help?"

Rich-world governments need to maintain or even increase foreign aid, which has saved millions of lives and helped many more people lift themselves out of poverty. It helps when policymakers hear from voters, especially in tough economic times, when they're looking for ways to cut budgets. I hope people let their representatives know that aid works and that they care about saving lives. Bono's group ONE.org is a great channel for getting your voice heard.

Companies—especially those in the technology sector—can dedicate a percentage of their top innovators' time to issues that could help people who've been left out of the global economy or deprived of opportunity here in the US. If you write great code or are an expert in genomics or know how to develop new seeds, I'd encourage you to learn more about the problems of the poorest and see how you can help.

At heart I'm an optimist. Technology is helping us overcome our biggest challenges. Just as important, it's also bringing the world closer together. Today we can sit at our desks and see people thousands of miles away in real time. I think this helps explain the growing interest young people today have in global health and poverty. It's getting harder and harder for those of us in the rich world to ignore poverty and suffering, even if it's happening half a planet away.

Technology is unlocking the innate compassion we have for our fellow human beings. In the end, that combination—the advances of science together with our emerging global conscience—may be the most powerful tool we have for improving the world.

Think Globally, Act Massively

The Bill & Melinda Gates Foundation focuses on catalytic philanthropy—invest­ments that can yield massive returns. That means finding areas where governments and private businesses aren’t innovating. Here are some of the founda­tion’s major activities over the past 15 years.

1999

Pledged $750 million to help set up the Global Alliance for Vaccines and Immuniza­tion (now the GAVI Alliance), supported by leading members of the world health community and experts in international childhood diseases.

1999

Gave $50 million to the Global Polio Eradication Initiative.

1999

Launched the Gates Millennium Scholars program to provide 1,000 low-income and minority students a year with scholarships and support for select advanced degrees at any college or university.

2000

Officially established the Bill & Melinda Gates Foundation, with a focus on health, education, and libraries.

2001

Pledged $100 million to the Global Fund to Fight AIDS, Tuberculo­sis, and Malaria—the first of $1.4 billion in commitments to an organization that has helped save more than 9 million lives.

2003

Announced the Grand Challenges in Global Health initiative to fund research that promises to greatly advance work against diseases that disproportionately affect people in the developing world.

2006

Created Agricultural Development, beginning with a $150 million joint investment with the Rockefeller Foundation, to establish the Alliance for a Green Revolution in Africa, which helps lift poor farmers out of poverty.

2009

Launched the Measures of Effective Teaching Project with 3,000 participating teachers to create better feedback and development systems for educators.

2010

Called on the global health community to declare this the Decade of Vaccines, with the goal of saving more than 20 million lives by 2020; pledged $10 billion to help develop and deliver vaccines.

2010

Launched the Next Generation Learning Challenges to push innovation that promotes personalized student learning.

2011

Hosted the GAVI Alliance pledging conference, which raised $4.3 billion from governments, philan­thropists, and the private sector to help immunize nearly 250 million of the world’s poorest children by 2015.

2011

Offered a $42 million reward for the invention of a toilet that can provide safe, affordable sanitation to the developing world while processing the waste into reusable energy, fertilizer, and fresh water.

2012

Joined 13 pharmaceutical companies, the US, UK, and UAE governments, the World Bank, and various global health organizations in a coordinated push to eliminate or control 10 neglected tropical diseases by the end of 2020.

2012

Melinda Gates chaired the Landmark London Summit on Family Planning, which united global leaders to provide 120 million women in the world’s poorest countries with access to contraceptives by 2020.

2013

Supported a six-year, $5.5 billion effort to eradicate polio by 2018.

Courtesy of the Gates Family