This paper presents simple conditions for monopoly third-degree price discrimination to have negative or positive e¤ectson aggregate consumer surplus. Consumer surplus is often re-duced by discrimination, for example when total welfare (con-sumer surplus and pro…ts) falls. Surplus increases...

The paper shows how commodity taxes can provide insurance to consumers when the producer price is volatile. Specific and ad valorem taxes have differing roles. The optimal specific tax is positive when demand has some elasticity. The optimal ad valorem rate is zero when demand is unit-elastic,...