Alex Mindlin | NY Times | April 2, 2007

In 2006, the number of households with PCs that downloaded at least one song using free peer-to-peer software, like Limewire or BitTorrent, grew a modest 7.2 percent, reaching 14.9 million, according to figures released by the NPD Group, a market-research firm.

Meanwhile, the number of PC households that used royalty-paying services like iTunes Store shot up 65.8 percent to 12.6 million, meaning such services could soon become the most widely used method of downloading music.

But the average peer-to-peer household still downloads far more songs. Peer-to-peer networks yielded five billion downloads in 2006, whereas 509 million songs were downloaded from iTunes-style services.

The explanation may be, quite simply, that free downloads are easier to gorge on than downloads you have to pay for. But there are other reasons peer-to-peer users download so many songs, said Russ Crupnick, an analyst with NPD. Among them is the declining price and increasing size of hard drives. “When I talk to people who are involved in a lot of peer to peer, they’re running around with external hard drives,” he said.

NPD gathered its data from tracking software installed on 12,000 home PCs. The data was adjusted to reflect the Internet-using population, and then extrapolated to the roughly 70 million Internet-using households in the United States.