It seems intuitive to think that if you contribute more to an outcome, you should be more morally responsible for it. Some philosophers think this is correct. They accept the thesis that ceteris paribus one's degree of moral responsibility for an outcome is proportionate to one's degree of causal contribution to that outcome. Yet, what the degree of causal contribution amounts to remains unclear in the literature. Hence, the underlying idea in this thesis remains equally unclear. In this article, I will consider various plausible criteria for measuring degrees of causal contribution. After each of these criteria, I will show that this thesis entails implausible results. I will also show that there are other plausible theoretical options that can account for the kind of cases that motivate this thesis. I will conclude that we should reject this thesis.