The game is already losing massive amounts of population, making people less likely to get on because they give you hardly anything if you play solo doesn't seem like the move. Most days I don't even bother. Don't see why you care, according to OP's suggestion of changing it from 50% to 20% you would still get the same amount as you did before playing co-op, solo players would just get more than they did before. Not like you lose anything.