Where would I be able to get statistics regarding P2P file sharing

[Nocturnal]

such as statistics about napster or kazaa actually boosting cd sales because they listen to the music, and rather have it on cd etc etc.

or, statistics showing how much money a musician such as eminem makes a year. and how that downloading music does not interfere with his funds for buying stupid escalades and supporting his xtc habit.

so fourth and so on.

any websites are appreciated, preferrably reliable sources.