Back on July 31 of 2007, Apple said it had sold three billion songs, making it number 1 on the Web as a music download retailer. This also made Apple the third largest music retailer as a whole, surpassing Amazon and Target. Today Apple has sold more than four billion songs and is now the number 2 music retailer in the world, only behind Wal-mart. It is, of course, still number 1 on the Web.

What this shows is that iTunes is not just gaining ground, but is gaining ground faster over time, slowing down to a nice pace. Originally it took iTunes three years to reach one billion songs (from 2003-2006). Then it took only 11 months to gain another billion songs. Again, the third billion took a mere five months. Finally the last billion, getting up to four billion, took roughly six months. So iTunes shows that iTunes should be gaining around two billion songs sold per year.

This data does not count the movies, TV shows, podcasts, or games that are downloaded through iTunes.