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    Demand — OCR A-Level Economics

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    Demand explained

    This topic covers the fundamental microeconomic concept of demand, exploring the relationship between price and quantity demanded, the distinction between individual and market demand, types of demand, and the factors causing movements along or shifts of the demand curve.

    What to demonstrate

    1. Definition of demand
    2. Relationship between price and quantity demanded
    3. Distinction between individual and market demand
    Show all 7 objectives
    1. Identification of joint, competitive, and composite demand
    2. Explanation of movements along the demand curve (extension/contraction)
    3. Explanation of shifts of the demand curve (increase/decrease)
    4. Construction and accurate labelling of demand diagrams

    Demand exam tips

    Topic Overview

    Demand is a fundamental concept in microeconomics that refers to the quantity of a good or service that consumers are willing and able to purchase at various price levels over a given period. In OCR A-Level Economics, understanding demand is crucial because it forms the basis of market analysis, price determination, and the study of consumer behaviour. The law of demand states that, ceteris paribus, as price falls, quantity demanded rises, and vice versa, leading to a downward-sloping demand curve. This inverse relationship is driven by the income effect (changes in real purchasing power) and the substitution effect (consumers switching to cheaper alternatives).

    Demand is not just about price; it is influenced by a range of non-price factors, including consumer income, tastes and preferences, the price of related goods (substitutes and complements), advertising, and expectations of future prices. These factors cause shifts in the demand curve, distinguishing between a movement along the curve (caused by price changes) and a shift of the curve (caused by changes in other determinants). Mastery of demand is essential for analysing market equilibrium, elasticity, and the impact of government policies such as taxes and subsidies.

    In the wider OCR A-Level syllabus, demand connects to supply to form the market mechanism, and is a building block for topics like price elasticity of demand (PED), income elasticity of demand (YED), and cross-price elasticity of demand (XED). These elasticity concepts measure the responsiveness of demand to changes in price, income, and other goods' prices, respectively. Understanding demand also underpins consumer theory, including utility maximisation and the law of diminishing marginal utility, which explains why demand curves slope downward. For students, mastering demand is vital for tackling essay questions on market failure, government intervention, and the dynamics of competitive markets.

    Key Concepts
    • →Law of demand: As price falls, quantity demanded rises, ceteris paribus, due to the income and substitution effects.
    • →Movement along the demand curve vs. shift of the demand curve: Price changes cause movements; non-price factors (e.g., income, tastes) cause shifts.
    • →Determinants of demand: Income (normal vs. inferior goods), price of substitutes and complements, advertising, population, and expectations.
    • →Individual demand vs. market demand: Market demand is the horizontal summation of all individual demand curves.
    • →Utility and diminishing marginal utility: The additional satisfaction from consuming one more unit falls, explaining the downward-sloping demand curve.
    Marking Points
    • Definition of demand
    • Relationship between price and quantity demanded
    • Distinction between individual and market demand
    • Identification of joint, competitive, and composite demand
    • Explanation of movements along the demand curve (extension/contraction)
    • Explanation of shifts of the demand curve (increase/decrease)
    • Construction and accurate labelling of demand diagrams
    Examiner Tips
    • 💡Always ensure diagrams are clearly labelled with Price (P) and Quantity (Q)
    • 💡Use the term 'ceteris paribus' when explaining shifts in demand
    • 💡Practice drawing diagrams for different types of demand shifts to ensure accuracy
    • 💡Always use the phrase 'ceteris paribus' when explaining the law of demand to show you understand the assumption of other factors constant. This demonstrates precision and can earn you marks in definitions.
    • 💡When drawing diagrams, clearly label axes (Price on vertical, Quantity on horizontal), the demand curve (D), and distinguish between movements (arrows along the curve) and shifts (new curve labelled D1 or D2). Use a ruler for straight lines.
    • 💡For higher-mark questions, link demand to real-world examples, such as the impact of a rise in income on demand for luxury cars (normal good) versus own-brand baked beans (inferior good). This shows application and evaluation.
    Common Mistakes
    • Confusing a movement along the demand curve with a shift of the demand curve
    • Failing to label axes correctly (Price on Y-axis, Quantity on X-axis)
    • Incorrectly identifying the causes of shifts versus movements along the curve
    • Misconception: A change in price shifts the demand curve. Correction: A change in price causes a movement along the demand curve, not a shift. Only non-price factors shift the curve.
    • Misconception: Demand and quantity demanded are the same. Correction: Demand refers to the entire relationship between price and quantity (the whole curve), while quantity demanded is a specific point on the curve at a given price.
    • Misconception: All goods obey the law of demand. Correction: Giffen goods and Veblen goods are exceptions where demand may increase with price due to income effects or snob appeal, though these are rare.
    Frequently Asked Questions
    What is the difference between a movement along the demand curve and a shift of the demand curve?
    A movement along the demand curve occurs when the price of the good itself changes, leading to a change in quantity demanded. For example, if the price of coffee falls, you move down the curve to a higher quantity. A shift of the demand curve happens when a non-price factor changes, such as consumer income or tastes. For instance, if advertising makes coffee more popular, the entire curve shifts to the right, meaning more is demanded at every price.
    What are normal goods and inferior goods?
    Normal goods are those for which demand increases as consumer income rises, such as restaurant meals or new cars. Inferior goods are those for which demand decreases as income rises, because consumers switch to better alternatives. Examples include own-brand products or public transport. When income falls, demand for inferior goods increases. This distinction is important for understanding how demand shifts with economic cycles.
    How do substitutes and complements affect demand?
    Substitutes are goods that can be used in place of each other, like tea and coffee. If the price of coffee rises, demand for tea increases (shift right). Complements are goods used together, like printers and ink cartridges. If the price of printers falls, demand for ink cartridges increases (shift right). Understanding these relationships helps predict how changes in one market affect another.
    Why does the demand curve slope downwards?
    The demand curve slopes downwards due to the income effect and substitution effect. The income effect means that when a good's price falls, consumers' real purchasing power increases, allowing them to buy more. The substitution effect means that when a good becomes cheaper relative to substitutes, consumers switch to it. Additionally, the law of diminishing marginal utility explains that as you consume more, the extra satisfaction from each unit falls, so you only buy more if the price is lower.
    What is the difference between individual demand and market demand?
    Individual demand is the quantity of a good that a single consumer is willing and able to buy at various prices. Market demand is the total quantity demanded by all consumers in the market at each price. To derive market demand, you horizontally sum all individual demand curves. For example, if at £5, person A demands 2 units and person B demands 3 units, market demand is 5 units.
    Can demand ever increase when price increases?
    Yes, in rare cases. Giffen goods (e.g., staple foods for very poor consumers) may see demand rise when price rises because the income effect dominates: a price rise makes consumers so much poorer that they buy more of the staple and less of luxuries. Veblen goods (e.g., luxury cars) are status symbols where higher price increases desirability. However, these are exceptions; the law of demand holds for most goods.

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