this varies substantially across settings and is related to a third problem that individual interventions are almost always evaluated in isolation this generalized costeffectiveness analysis gcea makes it possible to explore all interventions and combinations incrementally with respect to a counterfactual of doing nothing murray evans acharya baltussen tantorres edejer et al operationally the counterfactual that has been adopted in applied studies is defined in terms of what would happen to population health if all interventions of interest that are being provided now were stopped