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Supply is the quantity of a good or service that producers are willing and able to offer for sale at a given price in a given time period. Free notes.
Understanding Supply is part of Supply in GCSE OCR Economics.
7 min
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41
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GCSE OCR
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Supply is the quantity of a good or service that producers are willing and able to offer for sale at a given price in a given time period. Free notes.
Use this lesson to stay inside Supply while connecting the detail back to the wider The role of markets and money topic.
Read the core explanations from Understanding Supply before testing yourself from memory.
Imagine you run a bakery in Manchester. Every morning you decide how many loaves of bread to bake and sell. The number you choose depends on lots of things — the price customers are willing to pay, how much flour costs, and whether your oven is working properly. This decision is what economists call supply.
Notice the key phrase: willing and able. A farmer might want to grow more wheat, but if they lack the land or machinery, they cannot increase supply. Similarly, a factory might have spare capacity but refuse to produce more if the selling price is too low to cover costs. Both willingness and ability must be present for supply to exist.
In your GCSE exam, always mention both 'willing' and 'able' when defining supply — this is a common place where students lose easy marks.
There is a basic rule in economics: when the price of a good rises, the quantity supplied increases (and vice versa), all other things being equal. This is called the law of supply. Why? Because higher prices mean higher potential profits, which encourages existing producers to make more and may attract new firms into the market.
Think of it this way: if the price of coffee in a cafe doubles overnight, the cafe owner would want to sell as many cups as possible to maximise profit. They might open earlier, hire extra staff, or buy a bigger coffee machine. The higher price creates an incentive to supply more.
Price is not the only thing that affects supply. Several other factors can cause the overall supply of a product to change. These are sometimes called the determinants or conditions of supply. When any of these factors change, the entire supply changes at every price level. Let's examine each one.
If it becomes more expensive to make something, firms will supply less of it (at every price). Costs of production include wages, raw materials, rent, and energy. For example, when UK energy prices surged in 2022, many British manufacturers faced much higher electricity and gas bills. Some cut production and a few smaller firms closed entirely — this reduced the supply of goods like steel and glass.
Conversely, if costs fall, supply increases. When the National Minimum Wage rises, labour costs go up for firms like restaurants and retail shops, which can reduce their supply. But if a firm finds a cheaper supplier of raw materials, its costs fall and it can afford to produce more.
Improvements in technology allow firms to produce more output with the same (or fewer) resources. This reduces the cost per unit and increases supply. For example, automation in UK car factories means robots can weld and paint car bodies faster and more accurately than humans, allowing Jaguar Land Rover to produce more vehicles per day. Online shopping technology has allowed retailers like ASOS to supply clothing to millions of customers without needing expensive high-street shops.
Taxes reduce supply because they increase the cost of production — firms need a higher price to cover costs plus tax. Subsidies increase supply because they lower costs — firms can afford to produce more at every price. The UK government's subsidies for electric vehicle battery factories (such as the planned Tata factory in Somerset) are designed to boost the domestic supply of EV batteries.
If more firms enter a market, total supply increases. If firms leave, supply decreases. The UK coffee shop market is a good example — the rapid expansion of chains like Costa, Greggs, and independent cafes has massively increased the supply of takeaway coffee over the past decade. On the other hand, when high-street shops close down (as many did during the pandemic), the supply of in-store retail services falls.
This factor is especially important for agriculture and primary industries. A drought in East Anglia can reduce the supply of UK-grown wheat. Flooding can destroy crops and disrupt supply chains. The unusually hot summer of 2022 reduced yields for many British farmers, lowering the supply of lettuce, carrots, and other vegetables. Globally, poor harvests in major grain-producing countries can reduce the supply of food imports to the UK, pushing up prices in supermarkets.
If producers expect the price of their product to rise in the future, they may hold back supply now in order to sell later at a higher price. Oil producers sometimes do this — OPEC countries have reduced current oil supply when they expect future demand (and prices) to increase. Conversely, if a technology firm expects the price of computer chips to fall next year, it may rush to sell its current stock now, temporarily increasing supply.
| Factor | Effect on Supply | UK Example |
|---|---|---|
| Costs of production rise | Supply decreases | Rising energy bills forced some UK steel producers to cut output in 2022 |
| Improved technology | Supply increases | Automation in Nissan's Sunderland car plant increased vehicle output |
| Indirect tax imposed | Supply decreases | Sugar tax (2018) raised costs for soft drink producers like Britvic |
| Government subsidy given | Supply increases | Subsidies for UK wind farm developers boosted renewable energy supply |
| More firms enter market | Supply increases | Growth of coffee chains increased UK coffee supply |
| Bad weather / natural disaster | Supply decreases | 2022 heatwave reduced UK salad crop yields |
| Expectation of higher future prices | Supply decreases now | Oil producers withhold supply expecting higher prices later |
The UK has a well-known housing shortage. Despite strong demand, the supply of new homes has been slow to increase. Why? Several supply factors are at work: planning restrictions make it slow and expensive to get permission to build (raising costs); there is a shortage of skilled construction workers (a labour cost issue made worse by Brexit); land prices are very high, especially in the South East; and building material costs surged after 2020. All of these factors hold back the supply of new housing.
The UK imports around 40% of its food. The supply of food in UK supermarkets depends on global weather patterns, transport costs, and international trade agreements. When the Suez Canal was blocked by a container ship in 2021, supply chains were disrupted and some products became temporarily scarce. Rising fertiliser costs (linked to the Russia-Ukraine conflict) increased costs for British farmers, reducing the supply of domestically grown food. Meanwhile, new post-Brexit border checks added time and cost to food imports from the EU.
The UK's energy supply comes from a mix of sources: natural gas, wind, nuclear, and solar. Government subsidies for renewable energy have increased the supply of wind and solar power significantly — the UK now generates over 40% of its electricity from renewables. However, the supply of natural gas depends heavily on global markets and pipelines, making it vulnerable to international events. The closure of ageing nuclear power stations (like Hinkley Point B in 2022) reduced nuclear supply, while the new Hinkley Point C project aims to boost it again.
Worked example: Explaining a Change in Supply
Explain two reasons why the supply of new-build houses in the UK has been slow to increase. [4 marks]
Method: Identify two factors, explain each with a chain of reasoning
Answer: The supply of new-build houses has been slow to increase because (1) rising building material costs have made construction less profitable, discouraging developers from building, and (2) a shortage of skilled construction workers has limited firms' ability to increase output.
Worked example: Evaluating the Impact of a Subsidy on Supply
The UK government announces a £500 million subsidy for renewable energy producers. Evaluate the likely impact on the supply of electricity in the UK. [6 marks]
Method: Analyse the positive impact, then evaluate with limitations
Answer: The subsidy will lower production costs for renewable energy firms, increasing the supply of electricity. However, the magnitude and timing of the increase depends on planning constraints, construction time, and whether the subsidy is large enough relative to other rising costs. The long-run impact is likely to be significant, but short-run supply may change little.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-24.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
The factors that affect supply are costs of production, technology, indirect taxes and subsidies, the number of firms in the market, weather and natural conditions, and expectations of future prices. When any of these change, supply changes at every price level.
The law of supply states that when the price of a good rises, the quantity supplied increases, and vice versa, all other things being equal. Higher prices mean higher potential profits, which encourages existing producers to make more and may attract new firms into the market.
A subsidy is a payment from the government to a producer, designed to lower costs and encourage production. For example, the UK government subsidises renewable energy producers to increase the supply of wind and solar power.
Supply is the quantity of a good or service that producers are willing and able to offer for sale at a given price in a given time period. Both willingness and ability (resources, capacity) must be present, so always mention willing and able when defining supply.
Improved technology increases supply because firms can produce more output with the same or fewer resources, reducing the cost per unit. Automation in UK car factories, for example, lets robots weld and paint car bodies faster, so more vehicles are produced each day.
If more firms enter a market, total supply increases, and if firms leave, supply decreases. The rapid growth of coffee chains like Costa and Greggs has massively increased the supply of takeaway coffee in the UK.
Indirect taxes, such as VAT or excise duties on fuel, raise production costs and reduce supply. Subsidies are government payments to producers that lower costs, so supply increases; for example, the UK subsidises renewable energy producers to increase the supply of wind and solar power.
The supply of new-build houses has been slow to increase because planning restrictions make building slow and expensive, there is a shortage of skilled construction workers, land prices are very high, and building material costs surged after 2020. These raise costs and limit firms' ability to build.
Higher costs of production, such as wages, raw materials, rent and energy, reduce supply at every price, while lower costs increase supply. When UK energy prices surged in 2022, some manufacturers cut production, reducing the supply of goods like steel and glass.
Bad weather reduces supply, especially in agriculture: a drought in East Anglia can reduce the supply of UK-grown wheat and flooding can destroy crops. The hot summer of 2022 reduced yields of lettuce, carrots and other vegetables.
If producers expect the price of their product to rise in future, they may hold back supply now to sell later at a higher price, as oil producers sometimes do. If they expect prices to fall, they may rush to sell current stock, temporarily increasing supply.
Supply must be both willing and able because firms need the resources and capacity to produce as well as the desire to sell. A farmer may want to grow more wheat but cannot without land or machinery, and a factory with spare capacity may refuse to produce if the price is too low.
UK food supply depends on global weather, transport costs and trade agreements, because the UK imports around 40% of its food. Rising fertiliser costs linked to the Russia-Ukraine conflict and post-Brexit border checks have both added costs and reduced supply.
A subsidy for renewable energy lowers producers' costs, so supply of electricity increases as existing firms produce more and new firms enter. However, wind farms take years to plan and build, so the long-run effect is likely to be much bigger than the short-run effect.