Digital music sales grew to 10% of all worldwide music sales in 2007, up from 6% the year before, In-Stat reports. The market researcher expects the figure to jump to a whopping 40% of the market by 2012. However, according to a Fierce Mobile Content post on the report, that expansive growth is dependent on the still relatively small market for full-track mobile downloads outside of Japan.

Faster networks, more DRM-free services and increased marketing for mobile music services will help the market grow. Unless obstacles get in the way, In-Stat expects full-track mobile downloads to rake in $4.2 billion a year by 2012.

(Image credit: Jupiterimages Unlimited)