
One of the most prominent criticisms of institutions is that they are epiphenomenal---that they put a name on behavior that would have occurred anyway. That is, some have argued that the good news about compliance is not necessarily good news about cooperation because treaties may simply screen rather than constrain.
But the one does not necessarily imply the other. That is, even if institutions merely screen without constraining, this may nonetheless give us cause to celebrate international institutions. Below, I discuss a result from a formal model in which institutions screen but do not constrain---a model where the willingness of any given state to comply with a cooperative outcome is the same regardless of whether they join the institution. But it is nonetheless true in this model that fewer states would cooperate in the absence of institutions. In other words, when assessing the impact of institutions, we have to be very clear about what our standards are (as Martin and others (1 and 2) have argued). There is an important distinction between the claim that institutions alter state preferences and the claim that they merely separate nice, trustworthy types from bad, untrustworthy types, and I do not wish to downplay it. But it is nonetheless true that screening matters.