Why does the quantity people want to buy fall as price rises, and what shifts the whole demand curve?
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.
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What this dot point is asking
The SQA wants you to state the law of demand, draw and read a downward-sloping demand 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 demand.
What demand means
In economics, demand is more than wanting something. It is the quantity of a good or service that consumers are willing and able to buy at each possible price over a period of time. Both conditions matter: a person might want a sports car (willing) but be unable to afford it (not able), so it is not demand. Demand backed by the ability to pay is called effective demand.
The law of demand and the demand curve
The central rule is the law of demand.
Plotted with price on the vertical axis and quantity on the horizontal axis, this gives a demand curve that slopes downwards from left to right. The slope makes sense for two reasons: at a lower price the good is affordable to more people and existing buyers want more, while at a higher price some buyers leave the market or buy less.
Movement along versus a shift of the curve
This is the distinction the SQA tests most often, so be precise.
The non-price determinants of demand
Several factors other than price shift the demand curve. National 5 expects you to know the main ones.
- Income. For a normal good, higher income raises demand (shift right); for an inferior good (e.g. own-brand value food), higher income lowers demand as people trade up.
- Tastes and fashion. Advertising, trends or health news that make a good more popular shift demand right; falling popularity shifts it left.
- Price of related goods. A rise in the price of a substitute (a good bought instead, like coffee for tea) raises demand for this good. A fall in the price of a complement (a good used with it, like cars and petrol) raises demand for this good.
- Population. A larger population, or a change in its make-up, raises demand for the goods that population buys.
Why this matters across the course
Demand is one half of how a market sets prices. Combined with supply in the next dot points, it determines the equilibrium price and explains why prices change when conditions change. Understanding shifts is also essential for the stimulus questions in the exam, where you must explain how an event (a tax cut, a fashion, a population change) moves the market.
Try this
Q1. State the law of demand. [2 marks]
- Cue. As price rises, quantity demanded falls, all else equal (an inverse relationship).
Q2. A new advertising campaign makes a drink fashionable. State whether this is a movement or a shift, and in which direction. [2 marks]
- Cue. A shift of the whole curve to the right (demand increases).
Q3. Define a complement and give an example. [2 marks]
- Cue. A good used together with another; e.g. petrol with cars, or printers with ink.
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 demand and explain why the demand curve slopes downwards.Show worked answer →
The law of demand states that, all else equal, as the price of a good rises the quantity demanded falls, and as the price falls the quantity demanded rises (1 mark for the inverse relationship, 1 mark for "all else equal"). The curve slopes downwards because at a lower price more consumers can afford the good and existing buyers want more of it, while at a higher price some buyers drop out or buy less (1 mark). There is an inverse (negative) relationship between price and quantity demanded (1 mark). Markers reward the inverse relationship and a clear reason for the downward slope.
SQA N5 past-style6 marksExplain three factors, other than price, that could increase the demand for a good.Show worked answer →
A rise in consumer income increases demand for a normal good because people can afford more (1 mark + 1 development). A change in tastes or fashion in favour of the good, perhaps from advertising, shifts demand to the right (1 mark + 1 development). A rise in the price of a substitute makes this good relatively cheaper, so buyers switch to it and its demand rises - or a fall in the price of a complement raises demand for the good used with it (1 mark + 1 development). Markers reward three distinct non-price determinants, each explained as causing a rightward shift, not just named.
Related dot points
- 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.
- 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.
- 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.
- Personal economics: choices about spending, saving and borrowing; sources of income; budgeting; and managing risk and uncertainty.
A focused answer to the SQA National 5 Economics content on personal economics, covering the spending, saving and borrowing choices individuals and families make, sources of income such as wages, rent, interest and profit, budgeting under scarcity, and how households manage risk and uncertainty.
- 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.
Sources & how we know this
- SQA National 5 Economics Course Specification — SQA (2026)
- National 5 Economics - Course overview and resources — SQA (2026)