The International Federation of the Phonographic Industry (IFPI) reported that global digital revenues were $5.6 billion in 2012. This represented about 9% growth from 2011 and accounted for 34% of total industry revenues[1].
Apple regularly reports iTunes as a separate revenue item and occasionally it also reports payments data for developers and app download rates. By interpolating the data published and combining it with some assumptions it’s possible to estimate the mix of revenues (and costs) associated with iTunes.
My yearly estimates are summarized below.

Note that I also included historic digital music industry revenues (as a line). I also included the following summary items:
