What Is a Price Floor? How a Minimum Legal Price Affects Markets

A market equilibrium is the price at which quantity supplied and quantity demanded are equal in a simple competitive model. If a government sets a price floor below that level, the rule may have little immediate effect because the market price is already higher. Economists call a price floor binding when it is high enough to prevent the market from settling at its ordinary equilibrium.

A binding floor raises the legal minimum price. At the higher price, sellers may want to offer more of the good while buyers want to purchase less. Quantity supplied can then exceed quantity demanded, creating a surplus. This is the basic model used to explain what a price floor is.

Agricultural price supports are a common textbook example. A government may try to protect farm incomes by preventing the price of a crop from falling below a certain level. If the floor is binding, farmers may produce more while consumers buy less, leaving extra output. Real policies often add purchase programs, production limits, or other rules to manage that surplus.

A minimum wage can be described as a price floor in the labour market because it sets a legal minimum hourly wage. The simple model predicts that a binding minimum wage could increase the quantity of labour supplied while reducing the quantity employers demand. In that model, the gap appears as unemployment.

Real labour markets are more complicated. Employers have hiring power, workers face search costs, jobs differ in quality, and higher wages can affect turnover, productivity, and spending. Because of these factors, economists study actual minimum wage changes rather than assuming one simple effect in every place. The size of any employment effect can depend on the level of the minimum, local conditions, and the workers and firms involved.

This makes a price floor a useful starting model rather than a complete prediction machine. The model helps you identify the direction of incentives. Evidence and policy details tell you how strongly those incentives appear in a particular market.

Sellers who successfully make sales at the higher legal price may receive more per unit. Buyers who still purchase must pay more, while some buyers may leave the market. If unsold goods accumulate, producers or governments may face storage, disposal, or subsidy costs. Those tradeoffs matter when judging whether a policy achieves its goal.

When answering what a price floor is, always ask two questions: where is the floor relative to equilibrium, and what happens to quantity supplied and quantity demanded at that price? If the floor is not binding, little changes. If it is binding, the simple model predicts excess supply.

Europe produced one of the best known examples of a price floor surplus. Under the Common Agricultural Policy, the European Economic Community guaranteed farmers minimum prices for products such as butter, milk powder, grain, beef and wine. When market prices fell towards those levels, public agencies stepped in and bought the produce. By the 1970s and 1980s these purchases had built up enormous stores, and newspapers began talking about butter mountains, grain mountains and wine lakes. The stocks had to be kept in cold storage, sold off cheaply, exported with subsidies or sometimes turned into industrial alcohol.

The episode shows the costs that the simple diagram leaves out. Taxpayers paid for buying and storing goods that consumers did not want at the guaranteed price, and subsidised exports pushed down prices for farmers in other countries. Policymakers responded in stages. Milk quotas, introduced in 1984, limited how much each farm could produce at the supported price, which tackled surplus directly. Later reforms reduced guaranteed prices and moved support towards payments to farmers that were less tied to how much they produced. The surplus mountains shrank as a result, which is a neat illustration of the model working in both directions.

Most price floors aim to protect sellers, but Scotland's minimum unit pricing for alcohol uses a floor to protect health. Since May 2018, alcohol in Scotland cannot legally be sold below a set price per unit, where one unit is 10 millilitres of pure alcohol. The level started at 50 pence and was raised to 65 pence in 2024. A 70 centilitre bottle of 40 per cent spirits contains 28 units, so it now cannot be sold for less than £18.20. Wales introduced a similar rule in 2020.

Here the fall in quantity demanded, which the textbook model treats as a side effect, is the whole point. The floor mainly affects the cheapest, strongest drinks, which are bought disproportionately by heavy drinkers. Evaluations in Scotland reported a fall in alcohol sales and an estimated reduction in deaths caused directly by alcohol. One notable feature is where the extra money goes. Unlike an alcohol tax, a minimum price does not directly raise revenue for the government. The higher price is kept by retailers and producers, which is one reason some economists argue that a tax increase could achieve similar aims.

Imagine a market where, at a price of P pounds, buyers want 90 minus P units and sellers want to supply 2P minus 30 units. The two match at a price of £40, where 50 units are traded. Now a floor of £50 is imposed. Buyers will take only 40 units at that price, but sellers would like to supply 70, leaving a surplus of 30 units. Sellers lucky enough to make one of the 40 sales gain £10 on each, an extra £400 compared with before, but 10 sales that used to happen no longer take place at all.

Those lost sales matter. At 40 units, the keenest remaining buyer still values one more unit at £50, while it would cost a seller only £35 to produce it, so each missing trade wastes value that both sides could have shared. Added up across the 10 missing units, this lost value, called deadweight loss, comes to £75. If the government instead promises to buy the unsold 30 units at £50 to protect producers, the bill is £1,500, and it still has to store or dispose of goods nobody wanted at that price. Numbers like these show why price supports can become expensive quickly.

A price floor is a legal minimum price. A floor below equilibrium may have little effect, while a binding floor above equilibrium can create a surplus because sellers offer more and buyers demand less. Use the basic model first, then look at the real market and policy design before deciding what the final outcome will be.