Actually percentages are an 'exact science'. How you gather data and interpret that data is where human error and bias comes into play.
Everyone needs to just get over it.
Seriously. Harden up.
It is designed that way to make you feel frustrated and want to speed up your game, the only way to do that is to pay. If you don't want to pay then you can and should expect very little advancement.
The sense of entitlement is disgusting. The lack of logic and the way feelings are put before logic is seriously disturbing. You're a weird bunch you 'increase the drop rate' whiners.