Pandora was detected with about 236 million "Session Starts" for the month of December, according to Ando Media's "domestic ranker" for U.S. Internet listening for the 6am to 8pm daypart, Monday through Friday. That number is up from nearly 215 million in November. But the real surge comes in Ando's other category, called "Average Active Sessions", akin to the AQH metric for terrestrial radio. Pandora's Average Active Sessions number grew from 585,000 in November tot 642,614 in December.

The CBS Radio family, including AOL Radio and Yahoo, continues to rank #2, with 52 million Session Starts and 168,410 Average Active Sessions. Clear Channel and its grouping of iHeartRadio and other assets ranks at #3, with nearly 31 million Session Starts and about 134,000 Average Active Sessions. The rest of the top ten, by Average Active Sessions: Citadel, the pureplay Slacker Radio, Entercom, ESPN Radio, Cox Radio, Cumulus, and Digitally Imported Inc. Read the latest December Internet Audio research from Ando Media here.