And most of them prefer to listen on PCs.
Nearly 20 million US consumers will download and listen to podcasts at least once a week by 2010, according to interviews with Bridge Ratings' "Podcast Panel." The firm interviewed general podcast users ages 15 to 64 in Los Angeles, San Francisco, Seattle, St. Louis, Chicago, Boston, Miami, Dallas, Atlanta and Washington, DC.
Based on extrapolations from the interviews, a projected seven million Americans download and listen to podcasts every week, with an additional 21.4 million listening to a minimum of four podcasts every month.
Bridge said that terrestrial radio marketing, branding and promotion of podcasts were directly linked to the growth.
eMarketer's own projections put the US podcasting audience at 18 million regular subscribers in 2011, with a total potential audience of 55 million. In that year, US advertisers will spend $400 million on podcast advertising.
The Bridge study also found that news and talk podcast listening enhanced radio listening. A statistically significant number of podcast listeners said they had started listening more to radio broadcasts as a result of listening to the podcasts produced by that station.
Just over half of respondents said that listening to podcasts affected their radio listening.
The study did not address how listening to podcasts that were not tied to a radio program affected listening habits.
The study revealed what many podcast listeners already know: You do not need an iPod or mp3 player to listen. A majority of podcast listeners said they are more comfortable listening on their PCs than on portable devices. Most felt it was too complicated or time-consuming to transfer podcasts to the devices.
Learn how podcasting can fit into your campaign. Read the eMarketer Podcast Advertising report.