What is 'Demand Theory'

Demand theory is a principle relating to the relationship between consumer demand for goods and services and their prices. Demand theory forms the basis for the demand curve, which relates consumer desire to the amount of goods available. As more of a good or service is available, demand drops and so does the equilibrium price.

BREAKING DOWN 'Demand Theory'

Demand is the quantity of a good or service that consumers are willing and able to buy at a given price in a given time period. People demand goods and services in an economy to satisfy their wants, such as food, healthcare, clothing, entertainment, shelter, etc. The demand for a product at a certain price reflects the satisfaction that an individual expects from consuming the product. This level of satisfaction is referred to as utility and it differs from consumer to consumer. The demand for a good or service depends on two factors: (1) its utility to satisfy a want or need, and (2) the consumer’s ability to pay for the good or service. In effect, real demand is when the readiness to satisfy a want is backed up by the individual’s ability and willingness to pay.

Built into demand are factors such as consumer preferences, tastes, choices, etc. Evaluating demand in an economy is, therefore, one of the most important decision-making variables that a business must analyze if it is to survive and grow in a competitive market. The market system is governed by the laws of supply and demand, which determine the prices of goods and services. When supply equals demand, prices are said to be in a state of equilibrium. When demand is higher than supply, prices increase to reflect scarcity. Conversely, when demand is lower than supply, prices fall due to the surplus.

The law of demand introduces an inverse relationship between price and demand for a good or service. It simply states that as the price of a commodity increases, demand decreases, provided other factors remain constant. Also, as the price decreases, demand increases. This relationship can be illustrated graphically using a tool known as the demand curve.

The demand curve has a negative slope as it charts downward from left to right to reflect the inverse relationship between the price of an item and the quantity demanded over a period of time. An expansion or contraction of demand occurs as a result of the income effect or substitution effect. When the price of a commodity falls, an individual can get the same level of satisfaction for less expenditure, provided it’s a normal good. In this case, the consumer can purchase more of the goods on a given budget. This is the income effect. The substitution effect is observed when consumers switch from more costly goods to substitutes that have fallen in price. As more people buy the good with the lower price, demand increases.

Sometimes, consumers buy more or less of a good or service due to factors other than price. This is referred to as a change in demand. A change in demand refers to a shift in the demand curve to the right or left following a change in consumers’ preferences, taste, income, etc. For example, a consumer who receives an income raise at work will have more disposable income to spend on goods in the markets, regardless of whether prices fall, leading to a shift to the right of the demand curve.

The law of demand is violated when dealing with Giffen or inferior goods. Giffen goods are inferior goods that people consume more of as prices rise, and vice versa. Since a Giffen good does not have easily available substitutes, the income effect dominates the substitution effect.

Demand theory is one of the core theories of microeconomics. It aims to answer basic questions about how badly people want things, and how demand is impacted by income levels and satisfaction (utility). Based on the perceived utility of goods and services by consumers, companies adjust the supply available and the prices charged.

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