Who pays a tax is determined not by the laws of Congress but by the law of supply and demand,” as Tyler and I say in Modern Principles. In particular, whether demanders or suppliers pay a tax is determined by the elasticities of demand and supply. The more elastic side of the market can better escape a tax, leaving more of it to be paid by the inelastic side. The same thing is true for a subsidy but in reverse, the inelastic side of the market gets the benefit of the subsidy. Virginia Postrel applies the idea to education and education subsidies.