Internet radio and streaming services accounted for nearly four out of 10 minutes heard by young listeners in the fourth quarter, according to new figures released by the NPD Group.
 
Internet radio services like Pandora and iHeartRadio accounted for 23% of listening time for consumers between the ages of 13 and 35, up six percentage points from 17% a year earlier. Digital files took up 15% of listening time, while on-demand services such as Spotify accounted for 14% of listening time.

Mobile is a key part of Internet radio engagement. NPD found that more than half of Pandora and iHeartRadio listeners used their mobile phones to access those services. Time spent on mobile is another issue, however. In its "Infinite Dial 2013" study, Arbitron found that 18% of smartphone owners use the devices for Internet radio on a daily basis compared to 32% who use them daily to listen to downloaded music.
 
Listeners over 35 had different habits than the younger demographic, according to NPD. AM/FM radio accounted for 41% of listening. Internet radio accounted for just 13% of the older group's listening. AM/FM radio is indeed a format for the middle-aged. According to Arbitron, the heavy radio user has a median age of 42 and spends a self-reported six hours and 23 minutes per day listening to AM/FM radio.
 
NPD found that Pandora is used by 39% of listeners from ages 13 to 35 and has a big lead over other streaming services. iHeartRadio is second with 11%. The free version of Spotify is third with 9%. All others are in the low single-digits: Grooveshark at 3% and Slacker, Pandora One (the paid subscription service), TuneIn, Last.fm and Xbox Music each at 2%. Arbitron also found that Pandora has a wide lead over its competitors. The "Infinite Dian 2013" study found that 47% of smartphone owners had downloaded the Pandora app, while 15% had downloaded iHeartRadio and 6% had downloaded Spotify.