The pricing of gasoline grades and the third law of demand

Alchian and Allen’s “third law of demand” states that as a fixed cost increases by the same amount for low- and high-quality goods, the ratio of the prices of high- to low-quality goods will fall and the quantity demanded of high quality goods relative to low quality goods will increase. We examine the more general hypothesis by estimating the ratio of the quantities of sales of premium to regular grade gasoline using the ratio of premium to regular prices, controlling for supply and demand factors. We find moderate evidence for the more general hypothesis.