Why are firms willing to produce more when prices rise, and what else shifts the whole supply curve?
Explain the law of supply, the supply curve, the difference between a movement along and a shift of the curve, and the non-price factors that determine supply.
A CCEA GCSE Economics answer 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 whole curve, and the non-price determinants of supply such as costs of production, technology, taxes, subsidies and weather.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
Supply is the producer's side of the market, and it mirrors demand. You must know the law of supply and why the supply curve slopes upwards, draw and read the curve, and separate a movement along it (caused by the good's own price) from a shift of the whole curve (caused by a non-price factor). You then need the non-price determinants of supply and the direction each shifts the curve. This Section 1 material combines with demand to determine the market price, so getting the mechanics exact here is essential.
The law of supply and the supply curve
Supply is the quantity of a good that producers are willing and able to offer for sale at a given price in a given period. The law of supply states that, other things being equal, as the price of a good rises the quantity supplied rises, and as the price falls the quantity supplied falls. Plotting price against quantity gives a supply curve that slopes upwards from left to right.
The curve slopes up for two reasons. First, a higher price means more profit per unit, so existing firms expand and new firms enter. Second, producing extra units usually pushes up costs per unit (overtime pay, less efficient machinery), so firms will only make those extra units if the price covers the higher cost.
Movement along the curve versus a shift of the curve
As with demand, this distinction is examined repeatedly and must be precise.
A movement along the supply curve happens only when the price of the good itself changes. A price rise causes an extension of supply (a move up the curve to a larger quantity); a price fall causes a contraction of supply (a move down the curve). The curve does not move.
A shift of the whole curve happens when a non-price factor changes. The entire curve moves right if more is supplied at every price (an increase in supply) or left if less is supplied at every price (a decrease in supply).
The non-price determinants of supply
A shift of the supply curve is caused by one of the following. CCEA expects you to know each and its direction.
- Costs of production. Higher costs (wages, raw materials, rent, energy) reduce supply (shift left); lower costs increase supply (shift right).
- Technology. Better technology raises productivity and cuts costs, increasing supply (shift right).
- Indirect taxes. A tax on a good adds to the cost of each unit, so supply falls (shift left).
- Subsidies. A government subsidy lowers the cost of supplying each unit, so supply rises (shift right).
- Number of firms. More firms in the market increases total supply (shift right); firms leaving reduces it (shift left).
- Weather and natural events. For farm goods, good weather raises supply (shift right); drought, flood or disease cuts it (shift left).
Why this matters
Supply only determines price when set against demand, which is the next topic. A firm or government action almost always works by shifting supply, so you must be able to say which way the curve moves and then read off the new equilibrium. Taxes and subsidies, which appear again under market failure and government policy, are simply supply shifts. Mastering the mechanics now means you can analyse any market event later with confidence.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA-style4 marksExplain why a supply curve normally slopes upwards from left to right.Show worked answer →
The supply curve slopes upwards because a higher price gives producers a greater incentive to supply.
One reason is profit: at a higher price each unit is more profitable, so existing firms expand output and new firms are drawn into the market. Award a mark for the link between higher price and higher profit incentive.
A second reason is that producing extra output usually raises costs per unit (for example, paying overtime), so firms only find it worthwhile to make those extra units if the price is high enough to cover the higher cost. Award a mark for this cost reasoning.
The best answers state clearly that the relationship is direct (price up, quantity supplied up) and that it is a movement along the curve, because it is the good's own price that has changed.
CCEA-style6 marksExplain how a fall in the cost of raw materials and a new tax on a good would each affect its supply curve.Show worked answer →
Both are non-price factors, so both shift the whole supply curve rather than causing a movement along it.
A fall in the cost of raw materials lowers firms' costs of production, so they are willing to supply more at every price. The supply curve shifts to the right (an increase in supply). Award marks for identifying lower costs and the rightward shift.
A new tax on the good raises the cost of supplying each unit, so firms supply less at every price. The supply curve shifts to the left (a decrease in supply). Award marks for identifying the tax as a cost and the leftward shift.
A strong answer notes that lower costs and a tax pull in opposite directions, and that both are shifts because neither is caused by the good's own price.
Related dot points
- Explain the basic economic problem of scarcity and unlimited wants, the factors of production, opportunity cost, and the production possibility frontier as a model of choice.
A CCEA GCSE Economics answer on the basic economic problem, covering scarcity and unlimited wants, the four factors of production and their rewards, opportunity cost, and how the production possibility frontier models choice, efficiency and economic growth.
- Explain the law of demand, the demand curve, the difference between a movement along and a shift of the curve, and the non-price factors that determine demand.
A CCEA GCSE Economics answer 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 whole curve, and the non-price determinants of demand such as income, tastes, substitutes and complements.
- Explain how equilibrium price and quantity are set where demand equals supply, how surpluses and shortages are cleared by price, and how shifts in demand or supply change the equilibrium.
A CCEA GCSE Economics answer on price determination, covering market equilibrium where demand equals supply, how surpluses and shortages move price back to equilibrium, the price mechanism and its rationing and signalling roles, and how shifts in demand or supply change equilibrium price and quantity.
- Calculate and interpret price elasticity of demand and supply, distinguish elastic from inelastic responses, explain the factors that determine elasticity, and link elasticity of demand to total revenue.
A CCEA GCSE Economics answer on price elasticity, covering the formula and calculation of price elasticity of demand and supply, the difference between elastic and inelastic, the factors that determine elasticity, and how the elasticity of demand affects a firm's total revenue when price changes.
- Explain market failure through externalities, merit and demerit goods, public goods and the under-provision or over-provision of goods, and evaluate government responses such as taxes, subsidies, regulation and provision.
A CCEA GCSE Economics answer on market failure, covering negative and positive externalities, merit and demerit goods, public goods and the free-rider problem, and the main government responses including indirect taxes, subsidies, regulation, bans and direct state provision.
Sources & how we know this
- CCEA GCSE Economics specification (7510) — CCEA (2017)
- CCEA GCSE Economics specification (Standard PDF) — CCEA (2017)