Youth clearly defined the on-demand demographic, as Arbitron was quick to point out. Twenty-two percent of the population at large owns MP3 players, according to Arbitron--but this figure rises to 42 percent among 12- to 17-year-olds. In radio consumption, 12 percent of Americans 12 and over have listened to radio over the Internet, while another Arbitron study released April 13th, titled "The Infinite Dial: Radio's Digital Platforms" indicates that online radio audience size falls precipitously with age: although online radio reaches 19 percent of Americans ages 18-34, that number slides to 15 percent for the 25-54 set, suggesting a heavy skew toward youth.

This study recalls earlier trends--resembling, for example, a Pew report on instant messaging from September 2004, titled "How Americans use instant messaging." The Pew report said that 62 percent of Internet users ages 18-27 used instant messaging services--but that number fell to 37 percent among users ages 28-39, followed by further declines with age.

The latest Arbitron study has interesting implications for different media, especially when compared to the earlier Arbitron report. According to the first Arbitron report, in radio there is little or no competition between on-demand service and "old-fashioned" AM-FM audiences--but the same may not be true for TV. The second study suggests that 40 percent of Americans, forced to choose, would ditch their television in favor of the Internet.

This news story is important. I recommend that everyone read it.