The graph is pretty bad by the way:
- it would be interesting to see data in a longer series from before 1999, something tells me that 1999 was an all time high for the record industry
- the 6 billion from 2009 is presented as if sales have become close to 0
- if you study the graph well you actually see that the sales are holding up pretty well until 2005-2006 (they didn't bother to propely show us the years on the x-axis), after that there is a sharp decline (economic crisis, anyone?)