Podcasts have grown significantly more popular since Apple iTunes started listing the audio and video downloads last year, according to a report released this week by Nielsen Analytics.

The study indicates that the growth of podcasts could have significant effects on advertising models and radio listener numbers in the near future, as web users turn away from traditional media for online news, entertainment and political commentary.

The report, "The Economics of Podcasting", found that more than 6 per cent of US adults, or nearly 9m web users, have downloaded at least one podcast in the last month. Of those, about 10 per cent are "heavy users", downloading eight or more podcasts weekly. Most podcast listeners download between one and three shows per week.