Demand — Edexcel A-Level Economics B

In traditional economic theory, the primary objective of consumers is to maximise utility, or satisfaction, from the goods and services they purchase, subject to budget constraints. Consumers make rational decisions at the margin, weighing the marginal utility of an additional unit against its opportunity cost. For example, a consumer deciding whether to buy a second coffee considers if the added satisfaction outweighs the benefit of spending that money elsewhere. However, consumer decisions are often influenced by bounded rationality, emotional factors, and social norms, meaning they do not always act as perfect utility maximisers. Understanding these objectives helps firms predict demand curves and set effective pricing strategies.

The demand curve is a graphical representation of the relationship between the price of a good or service and the quantity demanded by consumers over a given period, ceteris paribus. It typically slopes downwards from left to right, illustrating the law of demand: as price falls, the quantity demanded increases, and as price rises, the quantity demanded decreases. For example, if the price of a smartphone drops from £800 to £600, consumers are willing and able to buy more units, which is plotted as a downward-sloping line on a graph with price on the vertical axis and quantity on the horizontal axis. This curve helps businesses and economists visualise consumer behaviour and market potential.

Understanding the distinction between movements along a demand curve and shifts of the curve is crucial for market analysis. A movement along the demand curve is caused solely by a change in the price of the good itself, resulting in an extension (increase in quantity demanded) or contraction (decrease in quantity demanded). In contrast, a shift of the entire demand curve occurs when a non-price determinant of demand changes, such as consumer income, tastes, or the prices of substitute goods. For instance, a successful advertising campaign shifts the demand curve to the right, meaning more is demanded at every price, whereas a price cut merely causes a downward movement along the existing curve.

A shift in the demand curve occurs when non-price factors change, altering the quantity demanded at every price level. An outward shift represents increased demand, while an inward shift shows a decrease. Key factors include changes in the prices of related goods: if a substitute's price (e.g. coffee) rises, demand for tea shifts outwards; if a complement's price (e.g. printers) rises, demand for ink shifts inwards. Changes in real incomes affect purchasing power, shifting demand for normal goods outwards when incomes rise. Tastes, fashions, and successful advertising or branding campaigns increase consumer desire, shifting demand outwards. Finally, demographic changes, such as an increase in population size or an ageing population, shift demand for specific goods like healthcare.