>http://www.techdirt.com/articles/20110707/03264014993/riaa-accounting-how-to-sell-1-million-albums-still-owe-500000.shtml

Two interesting charts plotting how music sales have radically changed over the years. Absent are illegal downloads which are hard to quantify ;)

http://andrewsullivan.thedailybeast.com/2011/07/how-the-music-industry-has-changed.html