The Sources of Market Failure

A competitive market works because price carries all the information buyers and sellers need, and because the person deciding how much to buy or sell bears the full cost and gets the full benefit of that choice. Shoe markets fit this well: the buyer pays for the shoes, the seller bears the cost of making them, and nobody else is affected. Clean air does not fit this. A factory's smoke affects neighbors who never agreed to anything and whose costs do not appear in the factory's price. That gap between private incentives and total social cost or benefit is the root of every market failure.

There are four standard breaks. Market power lets a firm restrict output below the competitive quantity and charge above marginal cost, so some mutually beneficial trades never happen. Externalities mean a cost or benefit spills onto bystanders, so the price ignores part of the true cost or value, producing too much of something harmful or too little of something helpful. Public goods are non-excludable and non-rival, so firms cannot charge users and underprovide them, or nobody provides them at all. Asymmetric information means one side of a trade knows something the other does not, which can shrink or even collapse a market, as with used cars or insurance.

Unit 6 spends its remaining topics on these four causes one at a time, pairing each with its fix: taxes or caps for externalities, antitrust or regulation for market power, government provision for public goods, and signaling or regulation for information problems. But intervention is not automatic. If the cost of running a program exceeds the surplus it recovers, the cure itself wastes resources, so the efficient move is to compare recovered surplus against program cost before intervening.