Over 249 million Americans live on the three percent of land that constitutes our cities. More than half of America's income is earned in 22 metropolitan areas. And people live longer in New York City than anywhere else in the U.S. That being said, our nation continues to grapple with negative perceptions about cities. Images of loud, dirty, noisy, graffiti and crime-ridden urban wastelands persist. Economist Ed Glaeser wants to change that. He's convinced that cities make us better, and that the proof can be seen everywhere from Minneapolis to Shanghai. Glaeser is a professor at Harvard, senior fellow at the Manhattan Institute, and author of a new book: "Triumph of the City: How Our Greatest Invention Makes Us Richer, Smarter, Greener, Healthier, and Happier."