Trevor, great work, I got another approach performed on Android market. The problem with categories in app markets is that they are high level classifications. Therefore, considering them as niche doesn’t tell us much. I performed a functionality-based analysis. I think this gives us a more precise niche definition. Here is my analysis: http://www.drdacademy.com/?id=an-analysis-of-the-android-app...

By the way I don’t think fitting a curve on two points on your result plot is right. Normally, we need a reasonable sample size.