Apple had 63% unit share of the U.S. paid music download market in the fourth quarter of 2012, according to research firm NPD Group, followed by AmazonMP3 with 22%.
According to NPD’s surveys of consumers, 44 million Americans bought at least one song track or album download last year. The research firm said: "That number has remained relatively stable over the past three years, despite the rapid growth of Pandora and other music-streaming options." NPD estimates that average per-buyer spending on music downloads increased 6% year over year "due largely to increases in music purchasing by teens, along with an increase in the number of consumers purchasing both single song tracks and full albums." source: NPD statement