Weight of downloads on rates :)

I am still searching for a way to make rates more fair... [confused]

What do you think is a better ride?
One with a level rate of 8.15 and 317 downloads?
Or one with a level rate of 8.15 and 17 downloads?

Is there's any mathematic magical formula to give "weight" to a rate?
And what do you think of this idea??? [:p]