The role of markets in allocating resources | IGCSE Class 10 Economics Notes

This note covers how a market system brings buyers and sellers together to allocate scarce resources, what market equilibrium and market disequilibrium mean, the three key resource allocation questions every economy must answer (what, how and for whom to produce), and how the price mechanism provides answers to these questions.

What is a market, and who are the buyers and sellers?

A market is a set of arrangements that allows buyers and sellers of a good, service or resource to exchange with each other, whether or not they meet in a physical place.

Buyers and sellers can interact in a village market, a city shop, or through a telephone call or the internet; what matters is that the arrangement allows free exchange of commodities, not the physical location.

In every market there are two sides. Buyers are the households, firms or other economic agents who demand a good, service or resource and are willing to pay a price for it.

Sellers are the producers or owners of resources who supply the good, service or resource and wish to receive a price for giving it up.

Each decision-making unit, whether a single person, a household or a firm, has only some of the resources it needs and must obtain the rest through exchange with others in the market.

Because no individual or firm has unlimited resources, every buyer and seller faces scarce resources: resources that are limited in supply compared with the uses people would like to put them to.

This scarcity is the reason markets exist at all. If resources were unlimited, there would be no need for a system of exchange or prices, because everyone could simply have as much of everything as they wanted.

Markets differ in how many buyers and sellers take part and in what is traded. A local market serves a small area, such as a village or a neighbourhood, while a national market covers a whole country and an international market links buyers and sellers across countries.

Markets also differ in what is exchanged. A goods market trades physical, tangible objects such as food and clothing, while a services market trades intangible tasks such as teaching or medical care.

A factor market trades the resources used to produce other goods and services, such as land, labour, capital and enterprise. The labour market is the clearest example: households supply labour and firms demand it.

Whatever the type, the same principle holds: buyers and sellers meet through some arrangement, agree a price, and exchange. That exchange is what moves scarce resources from those who hold them to those who value them most.

How does a market allocate scarce resources?

Why societies need to allocate resources

An allocation of resources describes how much of each resource is devoted to producing each good or service.

Because resources are scarce, any society has to decide how to allocate them between competing uses, and a market is one way of doing this (the other being central planning by a government or authority).

In a market economy, most resources are owned by private individuals and firms, and the decisions about what to produce, how to produce it and for whom are taken by those private decision makers responding to prices.

In a centrally planned economy, a government or central authority plans the important activities and decides the allocation of resources directly.

In practice, all economies are mixed economies: some important decisions are taken by the government and most economic activity is conducted through markets. Economies differ mainly in how large a part the government plays.

How prices coordinate buyers and sellers

In a market system, goods and services exchange at a price that is mutually agreed between buyers and sellers. This price reflects, on average, society's valuation of the good.

If buyers demand more of a good than is currently supplied, the price tends to rise; a rising price signals to producers that society wants more of that good than is being produced, and producers respond by increasing output.

In this way, prices carry information across the whole market and coordinate the independent decisions of millions of buyers and sellers without any central authority telling them what to do.

Definition: market system. A market system is an arrangement in which the free interaction of buyers and sellers, guided by prices, decides what is produced, how it is produced and for whom it is produced, without a central planning authority.

Markets exist for goods and services (where households are buyers and firms are sellers) and also for resources such as labour (where, in the labour market, households supply labour and firms are the buyers, the opposite pattern from the market for goods).

What is market equilibrium?

Defining equilibrium price and quantity

A market is in equilibrium when the plans of buyers and sellers match exactly, so that the quantity buyers wish to buy at the prevailing price equals the quantity sellers wish to sell at that price.

The price at which this happens is the equilibrium price, and the amount bought and sold at that price is the equilibrium quantity.

Definition: market equilibrium. Market equilibrium is the situation where the quantity demanded of a good exactly equals the quantity supplied at the prevailing price, so there is no tendency for the price to change.

The equilibrium point on a demand-supply diagram

Graphically, equilibrium occurs where the market demand curve and the market supply curve cross. The demand curve shows how much buyers wish to purchase at each price (sloping downward, since buyers wish to buy more as price falls); the supply curve shows how much sellers wish to supply at each price (sloping upward, since sellers wish to supply more as price rises).

Only at their point of intersection do the plans of buyers and sellers coincide.

Price is on the vertical axis and quantity on the horizontal axis. An upward-sloping supply curve SS and a downward-sloping demand curve DD intersect at a single point.

The price at this point of intersection is the equilibrium price; the quantity directly below it on the horizontal axis is the equilibrium quantity.

At any price above this point, the supply curve lies to the right of the demand curve (more is supplied than demanded); at any price below it, the demand curve lies to the right of the supply curve (more is demanded than supplied).

Worked example 1. In a market for wheat, the market demand curve is Qd = 200 − p and the market supply curve is Qs = 120 + p, where Qd and Qs are in kilograms and p is the price per kilogram in $. Calculate the equilibrium price and quantity.

Answer: At equilibrium, Qd = Qs, so 200 − p = 120 + p. Rearranging, 2p = 80, so the equilibrium price p = $40 per kilogram.

Substituting back, Qd = 200 − 40 = 160 kg (and checking, Qs = 120 + 40 = 160 kg). The equilibrium quantity is therefore 160 kg.

What is market disequilibrium: excess demand and excess supply?

When the prevailing price in a market is not the equilibrium price, the market is in disequilibrium, and quantity demanded and quantity supplied are unequal. There are two possible cases.

Definition: excess demand. Excess demand exists at a given price when the quantity that buyers wish to buy is greater than the quantity that sellers wish to sell at that price.

Definition: excess supply. Excess supply exists at a given price when the quantity that sellers wish to sell is greater than the quantity that buyers wish to buy at that price.

Excess demand

If the prevailing price is below the equilibrium price, quantity demanded exceeds quantity supplied, so there is excess demand.

Some buyers who cannot obtain the good, or cannot obtain enough of it, are willing to pay more, so the price tends to rise.

As the price rises, quantity demanded falls and quantity supplied rises, moving the market back towards equilibrium.

Worked example 2. Using the same demand and supply curves as Worked example 1 (Qd = 200 − p, Qs = 120 + p), suppose the prevailing price is $25, which is below the equilibrium price of $40. Find the excess demand at this price.

Answer: At p = $25, Qd = 200 − 25 = 175 kg and Qs = 120 + 25 = 145 kg. Since Qd is greater than Qs, there is excess demand, equal to 175 − 145 = 30 kg.

This pushes the price upward, back towards the equilibrium price of $40.

Excess supply

If the prevailing price is above the equilibrium price, quantity supplied exceeds quantity demanded, so there is excess supply.

Sellers who cannot sell the quantity they want to sell are willing to accept a lower price, so the price tends to fall.

As the price falls, quantity demanded rises and quantity supplied falls, again moving the market back towards equilibrium.

Worked example 3. Using the same demand and supply curves, suppose the prevailing price is $45, which is above the equilibrium price of $40. Find the excess supply at this price.

Answer: At p = $45, Qd = 200 − 45 = 155 kg and Qs = 120 + 45 = 165 kg. Since Qs is greater than Qd, there is excess supply, equal to 165 − 155 = 10 kg.

This pushes the price downward, back towards the equilibrium price of $40.

Excess demand = Qd − Qs and Excess supply = Qs − Qd; in equilibrium both of these are zero, so equilibrium can also be described as the zero excess demand, zero excess supply situation.

What are the three key resource allocation questions?

Because resources are scarce compared with what people collectively want, every society (or economy) faces the same three central problems, usually summarised as three questions.

1. What to produce, and in what quantities? Every society must decide how much of each possible good and service to produce: for example, whether to produce more food or more luxury goods, more agricultural goods or more industrial goods, more consumption goods now or more investment goods (such as machines) that raise future production and consumption.
2. How to produce it? Every society must decide which resources and which technology to use in producing each good: for example, whether to use more labour or more machines, and which of the available production methods to adopt.
3. For whom to produce it? Every society must decide how the goods and services produced are distributed among its members: who gets more and who gets less, and whether to guarantee a minimum amount of consumption, or free basic education and health services, for everyone.

These are the central problems that any economic system, whether a market economy, a centrally planned economy or a mixed economy, must find some way of answering.

A market economy answers them through the free interaction of buyers and sellers, coordinated by prices, rather than through direct instructions from a central authority.

The three questions are linked by scarcity. Because resources are limited, choosing to produce more of one good means producing less of another, so every answer to "what" also carries an opportunity cost: the value of the next best alternative given up.

In a market economy, the answers are not fixed once and for all. As demand and supply change, prices change, and the answers to all three questions change with them.

How does the price mechanism decide what to produce?

Definition: price mechanism. The price mechanism is the process by which changes in prices, driven by changes in demand and supply, signal to producers what to produce, how to produce it and for whom, without any central direction.

When buyers demand more of a good than is currently being supplied, there is excess demand and the price of that good rises.

A rising price is a signal to producers that society wants more of this good relative to others, and because a higher price generally allows greater profit, producers are led to increase their production of it, often by shifting resources away from goods whose price is falling.

Conversely, when buyers demand less of a good than is being supplied, there is excess supply and the price falls.

A falling price signals that society wants less of this good, and producers have less incentive to continue producing as much of it, so resources tend to move away from that good towards goods with rising prices.

In this way, the rise and fall of prices across many different markets, each one responding to its own balance of demand and supply, continually re-signals which goods society wants more of and which it wants less of, and resources are reallocated between goods accordingly, without the need for a government or planning authority to issue instructions.

The same signalling works for resources. If the price of a resource rises, the firms that use it are pushed to economise on it, and the owners of that resource are encouraged to supply more of it. The price therefore directs scarce resources towards the uses where buyers are willing to pay most for them.

How does the price mechanism decide how to produce?

The price mechanism also sends signals about which resources and production methods are least costly. Resources such as labour and capital (machinery, tools) also have prices, for example the wage rate for labour.

A firm aiming to keep its costs down will tend to use more of a resource that is relatively cheap and less of a resource that is relatively expensive.

If the price of one input rises relative to another, for example if wages rise relative to the cost of machinery, producers have an incentive to substitute the now relatively cheaper input (machinery) for the now relatively more expensive one (labour), changing how the good is produced.

If an input price falls, firms have an incentive to use more of it.

In the market for labour itself, households are the suppliers of labour and firms are the buyers, the wage rate being the price at which labour is exchanged.

The wage rate is determined, like any other price, where the quantity of labour that households wish to supply equals the quantity of labour that firms wish to employ; a firm takes on labour up to the point at which the value of the extra output produced by one more unit of labour equals the wage it must pay for that unit.

If the wage rate changes, firms adjust how much labour, relative to other resources, they use in production.

This is why the same good may be produced in different ways in different places. Where labour is cheap relative to machinery, producers tend to use more labour; where machinery is cheap relative to labour, they tend to use more machinery.

How does the price mechanism decide for whom to produce?

The final allocation question is how the goods and services produced in the economy are distributed among its members.

In a market economy, this is largely decided by purchasing power: those who can and are willing to pay the market price for a good obtain it, and those who cannot or will not pay that price do not.

A person's purchasing power depends on their income, which in a market economy is itself largely determined through markets, for example the price (wage) that a person's labour fetches in the labour market, or the return earned on land, capital or other resources that a person owns.

Because incomes differ between individuals, the mix of goods and services that different people are able to obtain through the market also differs.

The "for whom" question is therefore closely tied to the distribution of income and of resource ownership across a society.

Societies that rely heavily on markets to answer the "for whom" question still often face the question of whether everyone's minimum needs, such as basic education and health services, are being met, which is one reason governments sometimes intervene in otherwise market-based economies.

It is worth stressing that the three questions are answered together. The same set of prices that tells producers what to make and how to make it also decides, through the incomes those prices generate, who can afford to buy the output.

Definition: purchasing power. Purchasing power is the amount of goods and services a person can buy with their income at prevailing market prices.

Going beyond the syllabus

These ideas extend the unit and are not needed for the questions on it. They show how demand and supply analysis can be carried further, and what happens when a government overrides the price mechanism.

What happens when demand and supply shift at the same time?

When both curves shift at the same time, the direction of change in quantity or price can sometimes be worked out for certain and sometimes depends on the relative size of the two shifts.

In other words, when both curves move the same way, the quantity effect is certain but the price effect is ambiguous; when they move in opposite directions, the price effect is certain but the quantity effect is ambiguous. The actual outcome depends on which shift is larger.

How do price ceilings and price floors affect a market?

Once a market is in disequilibrium, it is the free movement of price itself that restores equilibrium. In practice, governments sometimes intervene directly in prices rather than leaving this adjustment to the market.

A price ceiling is a government-imposed maximum price, set below the equilibrium price to make a good more affordable; because it holds price below the level that would otherwise balance the market, it creates persistent excess demand (a shortage), which may then be managed through rationing, and can encourage a black market in which some buyers pay more than the official price to obtain the good. Price ceilings of this kind are often imposed on necessary items such as wheat, rice, kerosene and sugar, with the resulting shortage distributed through ration coupons and fair price shops rather than left to the market alone.

A price floor is a government-imposed minimum price, set above the equilibrium price, for example to guarantee farmers or workers a minimum income; because it holds price above the market-clearing level, it creates persistent excess supply, which a government agricultural support scheme may need to buy up to prevent the price from falling back.

These controls illustrate what happens when a government overrides, rather than relies on, the price mechanism's own adjustment process. Economies differ in how heavily they rely on the price mechanism rather than government planning: some governments have played a substantial role in planning economic activity, though this role has been reduced considerably in recent decades as markets have been given a larger part in answering the "what, how and for whom" questions.

How do shifts in demand and supply change the equilibrium?

When a market is disturbed by a change in demand or supply, the equilibrium price and quantity change in a predictable direction. The two cases below are the ones most often asked about.

What happens when the demand curve shifts?

If the market supply curve stays the same and the demand curve shifts rightward (buyers want more at every price), the new equilibrium will have both a higher price and a higher quantity than before.

If the demand curve shifts leftward, both the equilibrium price and the equilibrium quantity fall.

For example, a rise in consumers' income raises demand for a normal good at every price, shifting its demand curve to the right and raising both its equilibrium price and quantity.

With the supply curve SS unchanged, the original demand curve DD₀ shifts rightward to DD₁.

At the old equilibrium price, the new demand curve now shows a larger quantity demanded than supplied, so there is excess demand; the price rises until the new demand curve DD₁ crosses SS at a new equilibrium, which lies above and to the right of the old one, giving both a higher equilibrium price and a higher equilibrium quantity.

What happens when the supply curve shifts?

If the market demand curve stays the same and the supply curve shifts rightward (sellers want to supply more at every price, for example because an input becomes cheaper or more firms enter the market), the equilibrium quantity rises but the equilibrium price falls.

If the supply curve shifts leftward (for example because an input becomes more expensive), the equilibrium quantity falls but the equilibrium price rises.

Notice the pattern: a demand shift moves price and quantity in the same direction, while a supply shift moves them in opposite directions.

How do the two shifts compare?

This table is a quick way to check an answer: if a question says buyers' incomes rose and nothing else changed, the demand row applies, so both price and quantity rise.

Worked example 4. In a market for wheat, the demand curve is Qd = 200 − p and the supply curve is Qs = 120 + p, with Q in kilograms and p in $. A rise in consumers' incomes shifts demand so that the new demand curve is Qd = 240 − p. Calculate the new equilibrium price and quantity, and compare them with the old equilibrium of $40 and 160 kg.

Answer: At the new equilibrium, Qd = Qs, so 240 − p = 120 + p. Rearranging, 2p = 120, so the new equilibrium price is $60 per kilogram.

Substituting back, Qd = 240 − 60 = 180 kg (and checking, Qs = 120 + 60 = 180 kg). The new equilibrium quantity is 180 kg.

Compared with the old equilibrium, the price has risen from $40 to $60 and the quantity has risen from 160 kg to 180 kg, which is what a rightward shift in demand with unchanged supply predicts.

Glossary

• Market: an arrangement that allows buyers and sellers of a good, service or resource to exchange freely, whether or not they meet in person.
• Buyer: an economic agent who demands a good, service or resource and is willing to pay a price for it.
• Seller: an economic agent who supplies a good, service or resource and wishes to receive a price for it.
• Scarce resources: resources that are limited in supply relative to the competing uses to which people would like to put them.
• Resource allocation: the decision about how much of each resource is devoted to producing each good or service.
• Market equilibrium: the situation in which quantity demanded exactly equals quantity supplied at the prevailing price.
• Market disequilibrium: a situation in which quantity demanded and quantity supplied are unequal at the prevailing price.
• Excess demand: the amount by which quantity demanded exceeds quantity supplied at a given price.
• Excess supply: the amount by which quantity supplied exceeds quantity demanded at a given price.
• Price mechanism: the process by which changing prices, driven by demand and supply, signal what, how and for whom to produce.
• Demand curve: a line showing the quantity of a good buyers wish to purchase at each possible price.
• Supply curve: a line showing the quantity of a good sellers wish to supply at each possible price.
• Normal good: a good for which demand rises as consumers' income rises.
• Purchasing power: the amount of goods and services a person can buy with their income at prevailing market prices.
• Price ceiling: a government-imposed maximum price set below the equilibrium price.

Common errors and misconceptions

• Misconception: a market must be a physical place such as a marketplace. Correct: a market is simply an arrangement allowing free exchange; buyers and sellers may interact by phone or online without ever meeting.
• Misconception: a shift in demand and a movement along the demand curve are the same thing. Correct: a change in the good's own price moves along the existing demand curve; a shift of the whole curve is caused by other factors, such as income or tastes.
• Misconception: excess demand and excess supply are permanent features of a market. Correct: in a free market without price controls, excess demand pushes price up and excess supply pushes price down, until equilibrium is restored.
• Misconception: at the equilibrium price, everyone who wants the good is able to get it. Correct: at equilibrium, every buyer who is willing and able to pay that price can buy the good; those who want it but cannot or will not pay go without, which is how the price mechanism rations a scarce good.
• Misconception: "what to produce", "how to produce" and "for whom to produce" are three separate, unrelated decisions. Correct: they are all answered together through the same system of prices and incomes within a market economy.
• Misconception: the price mechanism requires a government to set prices. Correct: the price mechanism works through the free interaction of buyers and sellers; prices are not set by a central authority, which is what distinguishes a market economy from a centrally planned one.
• Misconception: only money prices matter in the "for whom" question. Correct: what a person can obtain through the market also depends on their income, which itself depends on the price their own labour or other resources fetch in other markets.

Exam-style questions with model answers

Q1. A market for a good has the demand curve Qd = 300 − 2p and the supply curve Qs = 100 + 2p, where Q is in units and p is the price in $. Calculate the equilibrium price and quantity, and the excess demand at a price of $30. [4 marks]

1. At equilibrium Qd = Qs, so 300 − 2p = 100 + 2p, giving 4p = 200 and an equilibrium price of $50.
2. Substituting p = $50, Qd = 300 − 100 = 200 units, and Qs = 100 + 100 = 200 units, so the equilibrium quantity is 200 units.
3. At p = $30, Qd = 300 − 60 = 240 units and Qs = 100 + 60 = 160 units.
4. Since quantity demanded exceeds quantity supplied, there is excess demand of 240 − 160 = 80 units, which tends to push the price up towards $50.

Q2. Define 'market equilibrium'. [2 marks]

1. Market equilibrium is the situation where the quantity of a good that buyers wish to buy exactly equals the quantity that sellers wish to sell, at the prevailing price, so there is no tendency for the price to change.

Q3. Identify two ways in which buyers and sellers can interact without meeting in person. [2 marks]

1. Buyers and sellers can exchange goods or services by telephone, agreeing on price and quantity without meeting face to face.
2. Buyers and sellers can also exchange over the internet, where orders and payments are arranged online rather than at a physical location.

Q4. Explain two reasons why a market may experience excess supply at a given price. [4 marks]

1. If the prevailing price is above the equilibrium price, sellers wish to supply more than buyers wish to buy at that price, creating excess supply; sellers who cannot sell their desired quantity will be willing to lower their price, which pushes the market back towards equilibrium.
2. If the supply curve shifts rightward while demand is unchanged, for example because an input used in production becomes cheaper or more firms enter the market, sellers wish to supply more at every price than before, so at the old price there is now excess supply until a new, lower equilibrium price is reached.

Q5. Explain how a rightward shift in demand affects the equilibrium price and quantity of a good, assuming the supply curve is unchanged. [4 marks]

1. A rightward shift in demand means that, at every price, buyers now wish to purchase more of the good than before.
2. At the original equilibrium price, there is now excess demand, because quantity demanded at that price has risen while quantity supplied has not changed.
3. This excess demand causes some buyers to be willing to pay more, so the price rises.
4. As price rises, the new demand curve and the unchanged supply curve settle at a new equilibrium with both a higher equilibrium price and a higher equilibrium quantity than before.

Q6. Analyse the three key resource allocation questions that a price mechanism answers for an economy. [6 marks]

1. Every economy must decide what to produce and in what quantities, for example how much food, housing or luxury goods to produce; in a market economy, rising prices for goods in high demand signal producers to produce more of them, and falling prices for goods in low demand signal producers to produce less.
2. Every economy must decide how to produce each good, for example how much labour and how much machinery to use; the price mechanism answers this because producers substitute towards whichever input, among labour and capital, is relatively cheaper, to keep their costs down.
3. Every economy must decide for whom the goods produced are distributed; in a market economy this is answered through purchasing power, since a person's income, itself determined largely through the labour market and other resource markets, decides how much of the final output they can afford to buy.

Q7. Discuss whether the price mechanism answers the question "for whom to produce" in a fair way. [8 marks]

1. In a market economy, goods go to the buyers who are willing and able to pay the market price, so the answer to "for whom" depends on purchasing power.
2. A person's purchasing power depends on their income, which is set largely by the price their labour or other resources fetch in factor markets.
3. This can be seen as fair in one sense: buyers who value a good highly can signal this by paying for it, and producers respond to what consumers choose, without a central authority deciding who gets what.
4. It also gives people an incentive to work and to supply resources that others value, since a higher income buys more goods.
5. However, a market responds to demand backed by ability to pay, not to need, so a person on a low income may be unable to buy essentials such as food, housing or medical care.
6. Because the answer reflects existing differences in income and wealth, the price mechanism tends to carry those inequalities into the goods each household receives.
7. On balance, the price mechanism answers the "for whom" question efficiently, but whether the answer is fair depends on how evenly income is distributed in the first place, which is why many governments add measures that help low-income households.

Key takeaways

• A market is any arrangement, physical or otherwise, that lets buyers and sellers exchange goods, services or resources freely.
• Markets allocate scarce resources because prices coordinate the independent decisions of many buyers and sellers without central direction.
• Market equilibrium occurs where the demand curve and supply curve intersect, so quantity demanded equals quantity supplied.
• Excess demand occurs below the equilibrium price and pushes price upward; excess supply occurs above it and pushes price downward.
• Every economy faces three key allocation questions: what to produce, how to produce it, and for whom to produce it.
• The price mechanism answers "what to produce" through rising and falling prices signalling producers towards goods in higher demand.
• The price mechanism answers "how to produce" through the relative prices of resources such as labour and capital guiding which inputs firms use.
• The price mechanism answers "for whom to produce" through purchasing power, which depends on income earned through resource markets such as the labour market.

Test yourself

What is the difference between a buyer and a seller in a market?

A buyer demands a good, service or resource and is willing to pay a price for it; a seller supplies it and wishes to receive a price in exchange.

What happens to price when there is excess demand in a market?

Price tends to rise, because some buyers who cannot obtain the good at the current price are willing to pay more, until quantity demanded falls and quantity supplied rises to match.

What happens to price when there is excess supply in a market?

Price tends to fall, because sellers who cannot sell their desired quantity are willing to accept less, until quantity demanded rises and quantity supplied falls to match.

Name the three key resource allocation questions every economy must answer.

What to produce and in what quantities, how to produce it, and for whom to produce it.

How does a rise in the price of a good signal producers in a market economy?

It signals that buyers want more of that good relative to others, giving producers an incentive to increase production of it and shift resources towards it.

How does the price mechanism help decide how a good is produced?

Firms compare the relative prices of inputs such as labour and machinery and use more of whichever input is relatively cheaper, to keep production costs down.

What decides who gets how much of the goods produced in a market economy?

Mainly purchasing power, which depends on a person's income, itself largely determined by the price their labour or other resources fetch in other markets.