Android Market Rankings Shuffle

The rankings of apps in the Android Market changed quite a bit, I noticed yesterday. At first I thought it was a periodic bug. I've seen my apps mis-ranked due to glitches in the past. But this actually looks like it might be a permanent change, and it looks like it's probably due to a change in the ranking formula.

For at least the past week, Dominoes had been holding firm at #2 and Golf Solitaire at #4. Here are the new rankings as of yesterday:


Golf Solitaire is now #1, which is cool. But Dominoes slid all the way down to #6. So if this is a deliberate change to the system, what happened?

My guess is that they changed the relative weighting of both retention rate and customer ratings. Here are the stats for both apps (click image to view full-size):


Dominoes has over twice as many active installs, but a slightly lower retention rate and customer rating. And they're both the same price, so that shouldn't be a factor in their difference.

If this is an effort on Google's part to improve rankings by placing more emphasis on quality, then I suppose I'm pleased. I now have a #1 app again, and Dominoes is still selling well. If anyone else has noticed changes and has any further input or insight, please share in the comments.