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Aggregating Welfare Gains

I characterize the set of policy decision rules which, in addition to satisfying the standard Pareto condition and a weak anonymity requirement, utilize only information about the objective effects of a policy change and its associated profile of individual "welfare gains". I establish that, depending on the assumptions made about individual preferences, there is either no social decision rule that satisfies these requirements, or a unique one. I characterize the unique social decision rules under different common definitions of "welfare gains" and common assumptions about individual preferences.