????Posted by Philip Elmer-DeWitt

????The Mac and iPod slices shrank between '08 and '09. iTunes grew a bit. iPhone grew a lot.

????Source: Company reports

????Steve Jobs likes to describe Apple's (AAPL) business model as a stool built on three-legs: the Mac, the iPod and the iPhone.

????But a quick glance at the 2009 Form 10-K, which Apple filed on Tuesday, shows that it is now more like a four-leg chair, with a couple of wedge-shaped pillows on the side.

????The Mac and iPod still bring in the biggest part of Apple's total sales revenue — 37.7% and 22.1%, respectively — but their shares of the pie are shrinking.

????The iPhone, meanwhile, is rapidly catching up, thanks to unit sales that grew 78% and GAAP revenue (swelled by deferred revenue dating back to 2007) that grew 266%. The iPhone now accounts for 18.5% of Apple's sales, just behind the iPod.

????The fourth leg of the chair is the line item Apple calls "other music related products and services" but which is mostly iTunes Store sales — music, video and apps. It continues to grow at a steady pace and now represents about 11% of Apple's net sales.

????Spreadsheets summarizing Apple's revenue streams are pasted below the fold. Apple's 2009 Form 10-K is available as a pdf file here.

????Net sales by product in millions.

????Source: Apple 10-K report

????Share of total revenue by product.

????Source: Apple 10-K report