Should We Use Distributional Weights in CBA When Income Taxes Can Deal with Equity?

Kaplow (1996) and others argue forcefully in favor of using the standard cost-benefit test alone, without any distributional concern, given “standard simplifying assumptions.” This paper, on the contrary, demonstrates that distributional weights, equal to the social marginal utility of income, should be applied in cost-benefit analysis, given weak separability in public goods instead of in leisure. This result holds for linear as well as non-linear income taxes, and whether they are optimal or not. A correspondingly modified Samuelson rule is derived and more general policy recommendations discussed.