Apple's App Store is a behemoth. Launched several years ago, the iTunes marketplace has ballooned into a billion dollar economy, with 7 billion downloads and more than 300,000 apps. (It's been so lucrative that Apple is planning to open  a Mac app store in January.)
What does the store look like visualized? The folks at App of the Day  spent the last few weeks charting the store, and have created a helpful infographic to show everything from average ratings and prices to category breakdowns. For example, more than a third of all iTunes' apps are free. Books are one of the most downloaded segments, even though 79% are paid apps with a $5 average. The most expensive category? Medical apps, which are some of the least popular in the store.
Check out other interesting finds below: