As the MP3 digital music player market moves beyond early adopters who purchase multiple devices and upgrade regularly, the user base will steadily increase from 37 mln in 2006 to over 100 mln in 2011. JupiterResearch also finds that the installed base of mobile phones capable of playing MP3 quality songs will surpass the number of music devise users beginning in 2009, but actual usage of music phones is nascent in the US.