According to market research firm, NPD Group, Apple's iTunes is the second most popular music retailer in the U.S. following only Wal-Mart. The NPD Group released its annual MusicWatch survey this week ranking retailers on all music sold last year.
The group also concluded that legal music downloads now account for 10 percent of all music acquired in the United States. However the sharp increase in legal digital download revenues could not offset the declines in the CD sales which saw a net decline of 10 percent.
Overall, the iTunes Store has now more than 50 million customers and boasts of a catalog of more than 6 million songs. Apple says that it has further sold more than 4 billion songs on iTunes, and that on Christmas day of 2007 alone it sold more than 20 million songs. Apple said that iTunes has also expanded its share of the video market.