There was a book a while back called "
Bowling Alone" which talked about the changes in social behavior in the last thirty or so years. I think these statistics display some of the same changes.
1) Since the Walkman, music has become a much more personal endeavor - teens don't get together and spin the latest vinyl anymore. Therefore...
2) We are an on-demand society. Radio just doesn't cut it, so we buy what we want, pushing up sales.
3) The digital format makes sharing music more troublesome then trading tapes or vinyl, not to mention the modern enforcement of anti-piracy laws.
4) Internet marketing keeps these people in our face all the time. I couldn't tell you what Justin What's-his-name sings or sounds like, but I know his face thanks to the news outlets I use (Yahoo, CNN, Fox News, etc). It's unlike anything that has come before.
And to
Abstract's point about #1 songs/albums, I wonder what you would find if you compared staying power (i.e. weeks on the charts) between then and now?