"Over the period 1999 to 2003, DVD prices fell by 25% and the price of players fell in the US from over $1,000 to almost nothing," says Strumpf. "At the same time, CD prices went up by 10%. Combined DVD and VHS tape sales went up by 500m, while CD sales fell by 200m, so a possible explanation is that people were spending on DVDs instead of CDs."
From this report that shows that illegal downloading hasn't really hurt CD sales.
Thanks Boing Boing for boosting my humble ego.