FORTUNE — Most analysts skipped over it, but ever since January Asymco‘s Horace Dediu has been trying to wrap his mind around a change in the way Apple reports certain line items. For example, what used to be called “Other related music products and services” is now called “iTunes, Software and Services” and consolidates, for the first time (according to the latest  SEC Form 10-Q)

“Sales on the iTunes Store, the App Store, the Mac App Store, and the iBookstore, and revenue from sales of AppleCare, licensing and other services”

As a result of the change, what was a business that Apple ran at slightly above break even, has become — according to Dediu’s restatement of past earnings reports — a major revenue source, generating $13.5 billion a year. That’s more than the iPod line brings in, and at the rate it’s growing — 32% a year — iTunes et al. will overtake the Mac business sometime this year.

Having written and spoken (Counting leg stools, Bigger than U.S. Steel)  about the new iTunes, Dediu is working on an “iTunes Business Report” that he plans to sell at his new Asymco Store. Last Friday, he released some of that work, starting with the chart above that shows how the various iTunes components have grown over the past seven years.

He also took a stab at estimating the profit margins of each component. Bottom line: Dediu believes that the business is generating 15% operating margin on gross revenues. That’s more than $2 billion a year.

You can read all about it at “So long, break even.”