That's broadcast radio, as measured in the latest quarterly RADAR research. The metric of "hours listened per month" is a new statistic for Arbitron, derived at the request of subscribers. Recently, Pandora has been touting its own figures, not based on Arbitron's RADAR studies. Here's how they compare: Internet audio service Pandora says users were logged in to its ad-supported free service for 2.1 billion hours in the third quarter of last year. (Fourth quarter results are not yet available.) That would suggest monthly usage of about 700 million hours to Pandora. It is by far the largest Internet radio service, whether pure-play or broadcasters-that-stream. Its 700 million hours is about 4.8% of the listening that Arbitron finds for broadcast radio.

More from a new 10-page Arbitron "Radio Today" presentation about broadcast radio:

- It reaches 90% of all Americans 12+ during the "prime shopping hours" of 6am to 7pm.
- 70% of Americans "tune in to radio each day for nearly 2 hours and 45 minutes."
- Radio reaches 91% of voters.
- Radio reaches 95% of all Hispanics on a weekly basis, and 93% of all African-Americans.

See the latest from Arbitron here.