Do you think that Google tracks the productivity or their Adsense publishers, or that this might be something they implement in the future? Does your payout per click have anything to do with the quality of your traffic? Do they know which sites send quality traffic and which send non-productive traffic? Any views?
If I had a chain of hardware stores and store A sold 4 times more hammers than store B I would be sending my more expensive (higher profit margin) hammers to store A. Don't see why google wouldn't do the same thing.
They certainly do. Their top producers get more options and controls over the display of ads among other features.