0455 · 2.4Price determination

Price mechanism and resource allocation

0:00Imagine a café selling sandwiches during lunchtime. A low price could leave customers queuing after the sandwiches have sold out. Set the price too high, and the café could finish lunch with unsold food. These situations show how markets determine prices and how those prices guide the use of resources. By the end of this video, you will understand why shortages push prices upwards and surpluses push them downwards. We will find an equilibrium using a table, then show exactly the same relationship on a diagram.

0:27We will also connect prices to decisions about what to produce, how to produce, and who receives the output. We need two starting ideas from demand and supply. Quantity demanded is the amount consumers are willing and able to buy at a given price. Producers, in turn, are willing and able to sell an amount called quantity supplied at that price. Both must refer to the same product, market and time period.

0:50Usually, a lower price encourages consumers to buy more, while a higher price encourages producers to offer more. We assume other influences remain unchanged when comparing different prices. That allows us to focus on movements along the existing demand and supply curves. Neither curve shifts in this video. The price mechanism allocates resources through the interaction of demand and supply. Prices communicate information and give consumers and producers incentives to change their decisions.

1:16No single person needs to organise every purchase or production choice. Instead, buyers and sellers respond to the prices they face. In this way the price mechanism answers the basic resource allocation decisions. On what to produce, firms have an incentive to provide goods consumers demand at a profitable price. If customers will pay enough to cover production costs and provide profit, supplying that product becomes attractive. Workers, equipment and materials can then be directed towards producing it.

1:43For how to produce, firms have an incentive to choose the lowest-cost production method for their intended output. The prices of labour, machinery and materials help them compare alternatives. A café might reduce ingredient waste because wasted food raises its costs. Here, saving resources can support both lower costs and environmental sustainability. The decision about for whom to produce concerns who receives the goods and services. Through the price mechanism, output goes to consumers who are willing and able to pay.

2:10Wanting a product is not enough without the purchasing power to obtain it. This answers who to produce for, but does not guarantee that everyone’s needs are met.

Finding equilibrium from a schedule

2:17A market price therefore influences both buying and selling decisions. However, some prices leave buyers wanting more than sellers offer. Others leave producers holding more than customers want. To find the price that balances these decisions, we compare quantities demanded and supplied. For example, this schedule describes a market for sandwiches during one lunchtime. At one dollar each, quantity demanded is one hundred sandwiches and quantity supplied is thirty. Raise the price to two dollars, and customers want eighty sandwiches while sellers offer forty-five.

2:49The table records planned purchases and sales, rather than guaranteeing that every intended transaction happens. Both quantities are sixty sandwiches when the price is three dollars. If the price is four dollars, quantity demanded falls to forty sandwiches while quantity supplied reaches seventy-five. At the top price of five dollars, buyers want twenty sandwiches and sellers offer ninety. Notice that the two quantities change in opposite directions as the price rises.

3:14Market equilibrium occurs where quantity demanded equals quantity supplied, so there is no tendency for price to change. Look for the row where the two quantities match. In our example, that happens at three dollars. The equilibrium price is therefore three dollars per sandwich, and the equilibrium quantity is sixty sandwiches per lunchtime. At this price, buyers want exactly the amount sellers offer. There is no shortage encouraging customers to bid more, and no surplus encouraging sellers to cut their prices.

3:41That explains why the price has no tendency to change. This conclusion assumes the other conditions affecting demand and supply remain unchanged. Equilibrium does not mean every person gets everything they want. Some customers may be unwilling or unable to pay three dollars. Nor is it the largest quantity producers could ever sell. It means that planned purchases and planned sales match at the current price.

Equilibrium diagrams and shortages

4:03We can represent the same market using a diagram. Put price on the vertical axis and quantity on the horizontal axis. Draw demand sloping downwards and supply sloping upwards, then label both curves clearly. Their intersection represents equilibrium because both curves show the same quantity at that price. From the intersection, draw a dashed horizontal line to the price axis. This identifies the equilibrium price of three dollars. A dashed vertical line down to the quantity axis identifies sixty sandwiches per lunchtime.

4:32The diagram and schedule are two ways of showing the same relationship. Market disequilibrium occurs at any price where quantity demanded does not equal quantity supplied. The mismatch creates either a shortage or a surplus. These are not separate demand or supply curves. They describe the difference between the quantities buyers and sellers choose at a particular price. Suppose the price is two dollars, below equilibrium. The schedule shows quantity demanded of eighty sandwiches and quantity supplied of forty-five.

4:59Buyers therefore want more than sellers are offering. This is excess demand, also called a shortage. To calculate its size, subtract quantity supplied from quantity demanded. Eighty sandwiches minus forty-five sandwiches gives a shortage of thirty-five sandwiches. This is the amount of demand left unmet at that price. It is not the total quantity customers want, because sellers are already offering some sandwiches. On the diagram, follow the two-dollar price line horizontally.

5:26It reaches the supply curve at forty-five sandwiches and the demand curve at eighty. The horizontal gap between these points represents the shortage. We measure across the graph because we are comparing quantities at one price. With more buyers than the available supply can satisfy, sellers have an incentive to raise their prices. Customers competing for the limited sandwiches may be willing to pay more. As the price rises, quantity demanded contracts while quantity supplied extends.

5:52The shortage narrows until both quantities reach sixty sandwiches at three dollars. This adjustment involves movements along the existing curves. It is not an increase in demand or supply, which would require a curve to shift. The higher price changes the quantity chosen on each curve. Keep the cause of the movement separate from changes in other market conditions.

Surpluses and price adjustment

6:11Now suppose sellers charge five dollars, above equilibrium. Quantity supplied is ninety sandwiches, but quantity demanded is only twenty. Producers are offering more than consumers want to buy. This is excess supply, also called a surplus. For a surplus, subtract quantity demanded from quantity supplied. Ninety sandwiches minus twenty sandwiches leaves a surplus of seventy sandwiches. On the graph, the demand intersection lies to the left of the supply intersection.

6:38Their horizontal separation shows the amount offered beyond what buyers want at five dollars. Sellers facing unsold sandwiches have an incentive to reduce the price. A lower price attracts additional purchases and makes supplying such a large quantity less attractive. Quantity demanded extends, while quantity supplied contracts. The surplus disappears when the market reaches three dollars and sixty sandwiches. The order of subtraction differs between a shortage and a surplus.

7:05In both cases, take the smaller quantity from the larger to measure the unmet demand or unsold supply. The names tell us which side is larger. Always identify that relationship before calculating, rather than relying on the order of the table’s columns. A price above equilibrium always creates a surplus, even when the product feels expensive. Higher prices discourage purchases while encouraging sellers to offer more. Similarly, only a price below equilibrium creates a shortage.

7:31A low price attracts more customers than the available supply can satisfy. Another common mistake is measuring disequilibrium as a vertical gap. A shortage or surplus is measured in units of the product, not dollars. You must compare the two quantities at the same price. The vertical distance from that price to equilibrium shows a price difference instead. Prices do not necessarily adjust instantly in real markets. Sellers may need time to recognise unsold stock or unmet demand.

7:58The model identifies the direction of pressure when prices can adjust. It explains why a shortage pushes price upwards and a surplus pushes it downwards.

Exam answers and recap

8:07In an examination, a table question might ask you to state the equilibrium price and quantity. State means express in clear terms, so give both values with their units. A define question wants the precise meaning of a term such as market disequilibrium. When the command word is explain, set out the reasons why or how the result occurs. For example, using our sandwich schedule, explain why a price of five dollars tends to fall.

8:31Start by comparing the quantities at that price. Then connect the mismatch to sellers’ decisions, rather than merely naming a surplus. Finish with the price outcome the question asks you to explain. At five dollars, quantity supplied is ninety sandwiches and quantity demanded is twenty sandwiches. There is therefore a surplus of seventy sandwiches. Sellers cut their prices to attract buyers and sell the unsold output. As a result, the price falls until it reaches the equilibrium of three dollars.

8:58An analyse question requires you to examine the relationships in detail. You could continue that explanation by showing how the falling price extends quantity demanded and contracts quantity supplied. In multiple-choice questions, test each proposed answer against the quantities at the stated price. For diagram questions, labelled axes and clear projection lines make your reasoning visible. The central idea is that buyers and sellers respond differently to price. Equilibrium is where quantity demanded equals quantity supplied, with no tendency for the price to change.

9:29Below that level, a shortage creates upward pressure. A price above equilibrium produces a surplus and downward pressure. These price signals also guide the allocation of resources. Firms choose goods consumers demand at profitable prices and seek the lowest-cost production methods. Output goes to those willing and able to pay. Understanding these connections lets you explain price determination rather than simply memorise where two curves cross.