Sales of physical albums fell by 18% in the US in 2008

"Album sales dropped a gaping 14 percent in 2008, according to figures shared by Nielsen Soundscan. Specifically, physical and digital albums collectively moved to 428.4 million units in the United States, from 500.5 million in 2007. The downward driver was the physical album, down 18.2 percent on the year. Digital albums jumped 32 percent to a record 65.8 million, though the gains failed to compensate for the broader physical declines."
Source: Digital Music News, 4th January 2009, citing data from Nielsen Soundscan