(CNN) Former President Barack Obama delivered this keynote address Wednesday during an event sponsored by Bill and Melinda Gates' organization that marks the release of a report tracking progress on global development. These are his remarks, as prepared for delivery:

Thank you, Bill, for that introduction, but more importantly, thank you for the tireless efforts you and Melinda put in towards making this a better world. I've had a chance to meet some of the remarkable Goalkeepers here, and I can say you are all an inspiration to me. Whether it's girls' education, or global health, or climate change, you are setting a standard for the sorts of innovation, persistence, activism and heart that we need to change the world.

That's really what everyone's here today to talk about -- changing the world. And I won't talk long, because I look forward to sitting down with Bill and having a discussion.

I remember sitting down with Bill in Paris a couple years ago, where the world came together to hammer out an agreement to save the planet by taking meaningful action to tackle climate change. It's a threat that may define the contours of this century more than any other. But Bill saw it not only as a challenge, but as an opportunity. "Well, we're just going to have to go ahead and invent some new technologies" -- meaning, yes this is hard, but we can figure it out. That can-do spirit, rather than despair, is what's allowed us to see real progress in reducing the pace of carbon emissions increases in the U.S. And even if the federal government isn't engaged on this effort right now, it's because of efforts like Bill's, and a whole host of entrepreneurs, and universities, and cities, and states, that America and the world will ultimately meet this challenge.

My broader point is, you tend to believe someone like Bill when he says we can do something. That kind of optimism is infectious. And that's exactly what we need right now.

Yes, we face some extraordinary challenges. Economic inequality and a changing climate. Terrorism and mass migration. The rise of nationalist thought, xenophobic sentiment, and a populist politics that too often pits "us" against "them" -- a politics that threatens to turn good people away from the kind of collective action that has always driven human progress.

These challenges are real. They'll take a long time to solve. But that shouldn't discourage any of us from the belief that we can make a difference. It should inspire us to meet the moment. We just have to reject the notion that we are suddenly gripped by forces that we can't control, and embrace the longer, more optimistic view of history and the part that we play in it.

If you are skeptical of such optimism, let me say something that may sound controversial. By almost every measure, America is better, and the world is better, than it was 50 years ago, or 30 years ago, or even 10 years ago.

I know that statement doesn't seem to jibe with the steady stream of bad news and cynicism we're fed on television and Twitter. But it's true. Think about it. I was born at a time, for example, when women and people of color were systematically excluded from big chunks of American life. Today, women and minorities have risen up the ranks in business, politics, and everywhere else, even if there are still miles to travel, and laws and hearts and minds to change.

Just since I graduated from college, crime rates, teen birth rates, dropout rates, the share of folks living in poverty have dropped, in some cases dramatically. The share of Americans with college education -- that's up. Despite a massive global recession, in the final year of my presidency, the uninsured rate reached a new low, and the median household income hit a new high.

Worldwide, our progress is even more impressive. Bill can rattle off the stats better than I can, but over the past 100 years, we've come from a world where only a small fraction of women could vote to a world where almost every woman can. Since 1950, the global average life expectancy has grown by more than 20 years. Since 1990, we've cut extreme poverty and childhood mortality in half. Since 2000, we've evolved from a world without marriage equality to one where it's a reality in more than two dozen countries.

All of this is why, when I speak to young people, I often ask: if you had to choose one moment in history in which you could be born, and you didn't know ahead of time who you were going to be -- what nationality; what gender; what race; whether you'd be rich or poor -- what moment would you choose? You'd choose right now. Because the world has never been healthier or wealthier. Despite some ongoing conflicts, the world at large has never been more tolerant or less violent. Fewer people are dying young, and more people are living not only longer, but better. More girls are in school; more adults can read; more children get the vaccines they need. There has never been a better time to be a young person on this planet. There have never been more powerful, more accessible tools for each of you to make a difference in your world, than today.

These trends are real. They're not the result of mysterious forces or chance. They happened because countless people, toiling many years,chose to make this progress. Some, like Bill and Melinda, deployed great wealth and influence; others, like your earlier speaker, Justin Trudeau, occupied a public office. But far more were simply citizens -- workers, mothers, entrepreneurs, clergy, and community leaders who mobilized, and organized, and voted, and innovated, and pushed for change. They knew that they wouldn't get everything they wanted as fast as they wanted it. They knew that progress requires struggle, and perseverance, and discipline, and faith. They knew that sometimes, for every two steps forward, you take a step back.

And more than anything, that's what is needed today; the engagement of everyone who wants to see a better future for our children. To take one example -- here in America, over the past eight years, thousands upon thousands of Americans threw themselves into the collective effort of reforming our health care system. Maybe they had experience with a sick child, or crushing medical bills, or a parent lost to cancer. And against all odds, they made a difference. For the first time, more than ninety percent of Americans know the security of health insurance. Paying more for insurance, or being denied insurance because of a preexisting condition -- that's not a thing anymore. We got rid of that. People are alive today because we did. That's progress.

Yes, there are people trying to undo that hard-won progress, for the 50th or 60th time, with a bill that will raise costs, reduce coverage, and roll back protections for older Americans and people with pre-existing conditions -- the cancer survivor, the expecting mother, the child with asthma or autism for whom coverage will once again become unaffordable and out of reach.

All without any demonstrable economic, actuarial, or even human rationale for pushing such a bill. And yes, it may be frustrating that we have to mobilize every couple months to keep our leaders from inflicting real human suffering on their constituents. But that's how progress is won. On every issue, we have to stand up for each other, recognizing that progress is not inevitable, that it can be fragile, it's in need of constant renewal, and that our individual progress depends on the progress of others. It depends on whether or not ordinary citizens stand up, and muster the determination to try and try again, because they believe in that upward trajectory of the human story.

I believe that each of us can make a difference, and all of us ought to try. That's what I ask of you today. I ask you to reject cynicism and pessimism, and push forward, in whatever you do, with an infectious, relentless optimism. Not a blind optimism that ignores the scale and scope of our challenges -- but a hard-earned optimism that's rooted in stories of very real progress. The belief that our successes -- however small, however incomplete -- are successes all the same.

Because each new generation stands on the successes of the last -- and reaches up to bend the arc of history in the direction of more freedom, more opportunity, more justice. That's why I spent so much of my presidency convening young leaders in every continent I visited. And that's why I'll spend so much of my post-presidency doing everything I can to help train and prepare the next generation of leaders to take their own crack at changing the world. The Obama Foundation will be based in Chicago, but it will have projects, programs, and digital networks all over the globe. I'm hoping I'll get a chance to work with some of you. Because I have great faith in you, just as Bill and Melinda have, and I am certain that if we all keep pushing forward, America and the world will make even more progress in the decades to come.

Thank you all very much.