The 8.4 million iPods Apple shipped in 2004 accounted for nearly one third of all digital audio players last year, a recent report by research firm In-Stat found. Various models of the iPod made up 30.2% of the combined worldwide hard drive and flash-based music player market in 2004. 
The firm said revenue for MP3 players reached approximately $4.5 billion, “a remarkable increase of almost 200% over 2003.”

In the same report, In-Stat also said that “the exploding market” for portable audio players is expected to reach over 104 million units by 2009, up from 27.8 million units in 2004. “Drivers for this booming market include falling prices, the availability of legitimate subscription and pay-per-download online music sites, smaller hard disk drives, and increasing Flash memory capacities,” the firm said.