Why are producers willing to supply more as price rises, and what shifts the whole supply curve?
Supply: the law of supply, the upward-sloping supply curve, movements along the curve versus shifts, and the non-price determinants that shift supply.
A focused answer to the SQA National 5 Economics content on supply, covering the law of supply and the upward-sloping supply curve, the difference between a movement along the curve and a shift of the curve, and the non-price determinants such as costs of production, technology, taxes and subsidies, and weather that shift supply.
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What this dot point is asking
The SQA wants you to state the law of supply, draw and read an upward-sloping supply curve, tell the difference between a movement along the curve and a shift of the whole curve, and explain the non-price factors that shift supply.
What supply means
Supply is the quantity of a good or service that producers are willing and able to sell at each possible price over a period of time. Firms exist to make a profit, so the price they can get for a good is the main signal telling them how much to produce.
The law of supply and the supply curve
The central rule is the law of supply.
Plotted with price on the vertical axis and quantity on the horizontal axis, this gives a supply curve that slopes upwards from left to right. The slope makes sense because a higher price makes each unit more profitable, so existing firms expand output and new firms are attracted into the market; a lower price does the reverse.
Movement along versus a shift of the curve
As with demand, the SQA tests this distinction closely.
The non-price determinants of supply
Several factors other than price shift the supply curve. National 5 expects you to know the main ones.
- Costs of production. Higher costs (wages, raw materials, energy, rent) make supply less profitable and shift it left; lower costs shift it right.
- Technology. New, more efficient technology lets firms produce more at the same cost, shifting supply right.
- Indirect taxes and subsidies. A tax on a good raises the producer's cost and shifts supply left; a government subsidy lowers net cost and shifts supply right.
- Weather and natural events (for farming and primary goods). Good weather raises the harvest and shifts supply right; drought, flood or disease shifts it left.
Why this matters across the course
Supply is the other half of how markets set prices. With demand, it determines the equilibrium price and explains why a poor harvest or a new tax changes prices. The costs that shift supply link directly to the costs, revenue and profit dot point, and indirect taxes and subsidies connect to government finance later in the course.
Try this
Q1. State the law of supply. [2 marks]
- Cue. As price rises, quantity supplied rises, all else equal (a direct relationship).
Q2. New technology lowers a firm's production costs. State whether supply shifts left or right. [1 mark]
- Cue. Right - more is supplied at every price.
Q3. Explain how an indirect tax on a good affects its supply curve. [2 marks]
- Cue. It raises the producer's cost, so supply falls and the curve shifts to the left.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 specimen4 marksDescribe what is meant by the law of supply and explain why the supply curve slopes upwards.Show worked answer →
The law of supply states that, all else equal, as the price of a good rises the quantity supplied rises, and as the price falls the quantity supplied falls (1 mark for the direct relationship, 1 mark for "all else equal"). The curve slopes upwards because a higher price makes production more profitable, so existing firms produce more and new firms enter the market (1 mark). Price and quantity supplied have a direct (positive) relationship (1 mark). Markers reward the direct relationship and a profit-based reason for the upward slope.
SQA N5 past-style6 marksExplain three factors, other than price, that could decrease the supply of a good.Show worked answer →
A rise in the costs of production, such as higher wages or raw material prices, makes supply less profitable, so firms supply less and the curve shifts left (1 mark + 1 development). A new indirect tax on the good raises the cost to the producer, reducing supply (1 mark + 1 development). A poor harvest caused by bad weather, or a fall in available raw materials, reduces what can be produced and shifts supply left - alternatively, the removal of a subsidy raises net costs (1 mark + 1 development). Markers reward three distinct non-price determinants, each explained as causing a leftward shift, not just named.
Related dot points
- Demand: the law of demand, the downward-sloping demand curve, movements along the curve versus shifts, and the non-price determinants that shift demand.
A focused answer to the SQA National 5 Economics content on demand, covering the law of demand and the downward-sloping demand curve, the difference between a movement along the curve and a shift of the curve, and the non-price determinants such as income, tastes, the price of related goods and population that shift demand.
- Market equilibrium and the price mechanism: equilibrium price and quantity, surpluses and shortages, market clearing, and how prices change when demand or supply shifts.
A focused answer to the SQA National 5 Economics content on market equilibrium and the price mechanism, covering how demand and supply set the equilibrium price and quantity, surpluses and shortages away from equilibrium, the market-clearing process, and how the equilibrium changes when demand or supply shifts.
- Costs, revenue and profit: fixed, variable, total and average costs; total and average revenue; and profit as the reward to enterprise.
A focused answer to the SQA National 5 Economics content on costs, revenue and profit, covering fixed, variable, total and average costs, total and average revenue, and profit calculated as total revenue minus total cost, the reward to enterprise that drives firms to produce.
- The basic economic problem of scarcity, the need for choice, opportunity cost as the next best alternative given up, and the four factors of production.
A focused answer to the SQA National 5 Economics content on the basic economic problem, covering scarcity of resources against unlimited wants, why this forces choice, opportunity cost as the next best alternative given up, and the four factors of production: land, labour, capital and enterprise.
- Government finance: direct and indirect taxation, current, capital and transfer spending, and the circular flow of income.
A focused answer to the SQA National 5 Economics content on government finance, covering direct and indirect taxation, the purposes of taxation, current, capital and transfer government spending, and the circular flow of income showing how money moves between households and firms.
Sources & how we know this
- SQA National 5 Economics Course Specification — SQA (2026)
- National 5 Economics - Course overview and resources — SQA (2026)