Bill McKibben in the New York Review of Books:
Radio receives little critical attention. Of the various methods for communicating ideas and emotions—books, newspapers, visual art, music, film, television, the Web—radio may be the least discussed, debated, understood. This is likely because it serves largely as a transmission device, a way to take other art forms (songs, sermons) and spread them out into the world. Its other uses can be fairly pedestrian too: ball games and repetitive, if remarkably effective, right-wing commercial talk radio. Rush Limbaugh is the radio ratings champ; according to the industry’s trade journal he reaches 14.25 million listeners in an average week. Sean Hannity, working the same turf, trails him slightly.
But an equally large audience turns to the part of the dial where public radio in its various forms can be found. Public radio claims at least 5 percent of the radio market. National Public Radio’s flagship news programs, Morning Edition and All Things Considered, featuring news and commentary alongside in-depth reports and stories that can stretch over twenty minutes—are the second- and third-most-popular radio programs in the country, each drawing about 13 million unique listeners in the course of the week. These NPR shows have far larger audiences than the news on cable television; indeed, all four television broadcast networks combined only draw twice as large an audience for their evening newscasts.