The survey estimated that iTunes use has grown 241 per cent over the past year, from 6.1 million unique visitors in December 2004 to 20.7 million in December 2005.
The data also revealed that iTunes users form their own clear economic group with some strange tastes.
For example, the iTunes user's favourite drink is strong cider, followed by imported beer then US beer. They are 2.2 times as likely to own a Volkswagen, followed by an Audi or a Subaru.
"The rapid growth of iTunes is an important phenomenon in the online media marketplace," said Jon Gibs, director of media analytics at Nielsen NetRatings.
"Consumers have clearly indicated that they are eager to control their own music libraries, one song at a time."
ITunes users are also predominantly young. Consumers aged 12 to 17 are nearly twice as likely to visit the iTunes website and use the application as the average internet user.
They are also more likely to be male. The site's visitors are 54 per cent male and 46 per cent female.
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