 It is important to make a distinction between the Hicksian (per John Hicks) and the Marshallian (per Alfred Marshall) demand function as it relates to deadweight loss.After the consumer surplus is considered, it can be shown that the Marshallian deadweight loss is zero if demand is perfectly elastic or supply is perfectly inelastic.However, Hicks analyzed the situation through indifference curves and noted that when the Marshallian demand curve is perfectly inelastic, the policy or economic situation that caused a distortion in relative prices has a substitution effect, i.e.