Employing a general equilibrium framework, Blackorby and Murty [2007] prove that, with a monopoly and under one hundred percent profit taxation and uniform lump-sum transfers, the utility possibility sets of economies with unit and ad valorem taxes are identical. This welfare-equivalence is in...

This paper extends the standard model of optimum commodity taxation (Ramsey (1927) and Diamond-Mirrlees (1971)) to a competitive economy in which some markets are inefficient due to asymmetric information. As in most insurance markets, consumers impose varying costs on suppliers but firms cannot...