Obviously the music industry has gone to great lengths to try and ingrain the message that illegal downloads of music have significantly damaged their bottom line, but is there any irrefutable evidence that declines in sales for major labels are as a direct result of illegal downloads?
For example, growth in other media (such as video games) will have obviously eaten into the amount of money available teenagers have to spend on music. Also, the prevalence of the internet means that distribution is cheap and affordable for even smaller labels now (meaning there's less reason for artists to jump to bigger labels).
I ask especially in regard to today's marketplace, where there are plenty of online stores making music available to legally download (such as iTunes, Zune Marketplace, and eMusic).