«Internet listening to AM/FM radio stations grew substantially in the last reporting period from Arbitron, going from 4,684 quarter hours in the spring of 2006 to 20,331 quarter hours in the fall of 2006.

The increase in quarter hours coincides with the implementation of new diary instructions, effective in the fall of 2006, that identify internet and satellite radio as sources of listening for respondents to note in their diaries in addition to AM/FM radio, according to Arbitron.
Sixty-six percent of the quarter-hours that included an internet identifier for an AM/FM station identified a local station. Seventy-eight percent of these diaries that contained listening to the internet streams of local stations also contained listening to the over-the-air version of the station.

Despite the growth in internet listening, listening to AM/FM radio stations online still accounts for less than 1 percent of un-weighted quarter-hours overall in the 30 analyzed markets (from 0.11 percent in spring 2006 to 0.47 percent in fall 2006).»

fonte: Internet Listening to AM/FM Radio Stations Soars in Fall 2006 Media buyer planner, 11/06/07