Marginal utility, or the additional satisfaction from consuming more of a good, helps explain why consumers reallocate spending when income changes. A household may direct added income toward goods that provide greater additional satisfaction, while reducing the relative share devoted to less valued purchases. This adjustment changes the chosen bundle while remaining subject to the budget constraint.
A normal good becomes more strongly represented in consumption as income rises, whereas an inferior good may receive less spending because the household shifts toward alternatives it prefers at higher income. This distinction describes the income effect rather than a price response. Identifying the category helps explain why households with similar prices and preferences can change their consumption patterns differently.
An income-consumption curve traces the bundles selected at different income levels while prices and preferences are held as the relevant decision conditions. Its path shows how consumption changes as purchasing power expands or contracts, including shifts associated with normal and inferior goods. The curve therefore links individual utility maximization to observable patterns in household demand.
Begin by specifying the consumer’s income, the prices of goods, and the relevant preferences. Use income and prices to identify the affordable bundles, then determine which bundle provides the greatest utility. Repeat the comparison for different income levels and record the resulting choices. Comparing those bundles reveals income effects and supports construction of an income-consumption curve.
The framework compares the household’s feasible choices and utility before and after income changes caused by a policy or economic shock. A reduced budget may force reallocation toward different goods, while additional income can expand the set of affordable bundles. Examining the selected bundles indicates how the change affects consumption patterns and household well-being.
Individual utility-maximizing choices provide a basis for understanding demand because changes in income alter the bundles consumers select. When many households respond to income changes, their reallocations can influence broader market behavior. The analysis also clarifies why demand responses differ across goods, particularly when some are normal and others are inferior.