The Wall Street Journal has an article on Amazon.com's scant digital sales thus far (estimated at $100 million) even though it has invested an estimated $300 million over three years.

That article, and a post at Silicon Alley Insider, got me thinking about Amazon.com's MP3 sales and how they compared to those of iTunes.

First, I'd like to point out that iTunes did not sell two billion tracks last year as Silicon Alley Insider wrote today. Not in the U.S. and not globally (don't forget that there are many iTunes stores around the world). The numbers I have seen in the media peg iTunes' global 2008 sales at 1.7 billion. (This Billboard.biz post by Ed Christman has that estimate.) And since many of those downloads were from albums, it certainly did not sell two billion or 1.7 billion tracks at $0.99 each. (Note also that iTunes charges different amounts in different countries.)

Different versions of the iTunes store have been in multiple countries since mid-2004. Amazon.com didn't even announce an international rollout of its MP3 store until late Jan 08. So, as best we can, we should compared iTunes' U.S. sales to Amazon.com's MP3 sales.

According to Soundscan (numbers found in this post at Listening Station), there were 844 million single track downloads in the U.S. in 2007. There were an additional 50 million album downloads. If you count an album as ten tracks, that comes out to 1.344 billion downloads in the U.S. in 2007.

If iTunes has 80% market share, that means iTunes sold 1.075 million tracks in 2007. It has been reported that all iTunes stores sold 1.7 billion tracks in 2007. That puts iTunes' U.S. share at 63% of global if you assume it has 80% of the U.S. market, or 55% of global if you assume it has 70% of the U.S. market. (Billboard.biz estimated a 70% share for the U.S. in 2007.)

The Amazon.com MP3 store launched in late September 2007. So Amazon.com has been in the game for less than seven months. It's not going to compare well to iTunes in such a short period of time (regardless of the current Pepsi promotion). It does compares well to iTunes' first seven months of operation, in which it had only U.S. sales. iTunes was launched in late April 2003 and sold 30 million tracks by the end of the year.

NPD said iTunes' U.S. sales were 10x Amazon.com's in Feb 08. I figure iTunes U.S. did at least 100 million in Feb 08 (given last year's total and a modest 30% increase). At that multiple, Amazon.com did 10 million. With a small amount of growth throughout the year, that could total 150 million in 2008. Still small versus iTunes' U.S., which should do 1.2 billion to 1.3 billion in 2008.