correlated does not always mean causes...
The raw numbers of products made - albums, films - etc has gone up as filesharing has gone up. But is it causal?
Technology has greatly reduced the cost of production; you can do on a Mac what used to need kit worh 100s of thousands. Any fule can make an album with Logic (and the quality of most of it shows). This is a good thing, but it's not filesharing that's caused it.
Intrinsically costly productions - classical orchestral pieces for example - have almost certainly declined over the same period.