The just-issued December Webcast Metrics rankers for "domestic" usage covering 6am to 8pm weekdays show Pandora setting new marks. On January 5, Triton Digital announced Pandora had crossed the one-million-Active Sessions mark in the November data. Now the December numbers show Pandora up from 1,045,551 Average Active Sessions - somewhat like broadcast radio's AQH - to 1,143,060. Pandora's "session starts" swelled from 416 million to 455 million. Clear Channel continues pushing its iHeartRadio platform and other off-air listening, and it ranks #2, growing from about 168,000 Active Sessions to 178,000. Its Session Starts also grew, from 71.4 million to 76.7 million. Third place in the Triton Digital rankers goes to CBS, with Active Sessions dropping from about 97,000 to about 90,000, with the recent loss of AOL Radio. (CBS still includes Yahoo LaunchCast.) The latest Triton Digital top 20 rankers for December are here.