iTunes is continuing to increase its share of the digital music market in the US even in spite of Amazon MP3, the NPD Group found on Thursday. Amazon moved up 2.3 points from year-to-year to 13.2 percent of the American download market in the summer, but Apple climbed by an even higher amount, up three points to 66.2 percent. As a result, all of Amazon's gain came at the expense of smaller rivals, which combined were just 20.5 percent.
