This paper suggests that Nash equilibrium can be interpreted as a conceptual tool for addressing comparative-statics issues on an aggregate level. Together with additional assumptions, Nash equilibrium helps generate testable predictions about changes or differences of behavior induced by changes or differences of exogenous variables. However, Nash-equilibrium behavior, as such, is not subject to empirical testing. Instead, widespread and persistent behavior is modeled as a Nash equilibrium by assumption. The paper argues that this interpretation is in line with the traditional (...) use of an equilibrium concept in price theory. The suggested interpretation is illustrated with the model of public-goods provision. The paper compares this interpretation of Nash equilibrium with other interpretations and discusses its limits. (shrink)