Total Album Sales (physical + digital albums)
2009: 373.9 million
2008: 428.4 million
2007: 500.5 million
2006: 542.4 million
2005: 618.9 million
2004: 667 million
2003: 687 million
2002: 681 million
2001: 763 million
2000: 785 million
Sources: Billboard, USA Today, New York Times, Hollywood Reporter, CTV, BBC, WSJ.
Here's a little more data...
Track equivalent albums (where 10 track downloads equal one album)
2009: 489.8 million
2008: 535.4 million
2007: 585 million
2006: 646.3 million
2005: 654.1 million
2004: 680.7 million
Compact Discs
2009: 294.9 million
2008: 360.6 million
2007: 449.2 million
2006: 553.4 million
2005: 598.9 million
2004: 651.1 million
2003: 635.8 million
2002: 649.5 million
2001: 712.0 million
2000: 730.0 million
Digital tracks
2009: 1.16 billion
2008: 1.07 billion
2007: 844.1 million
2006: 582 million
2005: 353 million
2004: 141 million
2003: 19.2 million (SoundScan monitored them only during the year's second half)
Comments
Wow, an almost 50% drop from 2000 to '09. Man...it's going to be an interesting next few years.