Scarborough Research reveals that train riders and major urban walkers are especially likely to either own or plan to purchase an mp3 player. These commuters make up more than one-fifth of all consumers in Scarborough's 75 markets. (And you have to believe that as gas prices stay above $3/gallon, more Americans will join this group.) Of course, many of these rail/subway riders are more likely to fall into the 18-34 group as well.
As you may recall, focus groups we conducted for Arbitron last year revealed that some 18-34 respondents perceive that radio isn't portable. While they can take iPods anywhere, several indicated that radio is tethered to the car or the nightstand. While we were initially surprised to hear these statements, it sure is true that you just don't see Walkman's anymore. Try to find one in a Best Buy or other consumer electronic store. If they even stock them, they're buried in small racks at the back of stores. Carrying around an iPod is a fashion statement. Toting a Walkman (or a boom box!) says something entirely different about who you are.
But the big frontier is cell phones, an arena where radio must have presence if it is to regain its portability. Internet streaming will help get us there, yet another key reason why every terrestrial station needs presence on the World Wide Web.