A study from the BI Norwegian School of Management has found that those who download free music from services like BitTorrent are also the biggest legitimate consumers of downloadable music.
In fact, among all 1,901 (global?) study participants (all of whom were over the age of 15), it was found that those who downloaded "free" music were 10x more likely to download pay music. In other words, music pirates are the music industry's largest online consumers.
Note: "Free" music obviously implies pirated music, but it also encompasses legitimate free music download services.
The findings also included that, in the 15-20 age range, 50% of participants had bought a CD in the last six months. So that trusty format isn't dead quite yet.
Since we relied on Google's translation from the original Norwegian, anyone who speaks the language is encouraged to glean for more specifics and post them in the comments. [Survey and BMI Thanks Jon!]