Microeconomics is the branch of economics that studies how individual decision-makers, such as households, workers, firms and investors, choose what to buy, sell and produce, and how those choices meet in markets to set prices and quantities. Its central themes are scarcity, trade-offs and incentives: every choice has an opportunity cost, and people respond when costs and rewards change.
It is the counterpart of macroeconomics, which looks at economy-wide totals such as output, inflation and unemployment. The boundary is not sharp, because modern macro models are built on micro foundations. Microeconomics supplies the tools used in competition law, regulation, tax design, pricing strategy and much of everyday business analysis.
Microeconomics in plain terms
Picture a weekly farmers' market. Each shopper decides how many apples to buy given their budget and how much they like apples compared with pears. Each stallholder decides how many apples to bring and what to charge. By the end of the morning, a price has settled where the apples people want to buy roughly match the apples on the tables. Microeconomics studies that kind of scene: the individual decisions and how they fit together.
It also asks what happens when the scene changes. If a frost ruins half the harvest, or one stallholder buys out all the others, or the council adds a fee on every sale, microeconomics predicts who ends up paying more, who sells less and whether the market as a whole works better or worse.
Core topics
Most introductory and intermediate courses cover the same building blocks:
- Consumer choice. How people allocate a limited budget, using ideas such as marginal utility, income effects and the substitution effect.
- Production and costs. How firms combine factors of production, why costs rise or fall with scale (economies of scale), and why the law of diminishing returns limits adding more of one input. Decisions are made at the margin, comparing extra revenue with marginal cost.
- Markets and prices. Supply and demand, elasticity and how markets reach equilibrium.
- Strategic behavior. Game theory models situations where each party's best move depends on what others do, from price wars to auctions.
- Information and risk. How markets behave when one side knows more than the other, as in asymmetric information and moral hazard.
Market structures
A large part of microeconomics compares how markets perform depending on how many sellers there are and how easily new ones can enter. At one extreme is perfect competition: many small firms selling identical products, none able to set the price. At the other is monopoly: a single seller that can raise prices above cost. Between them sit oligopoly, where a few large firms watch each other closely, and monopolistic competition, where many firms sell slightly different products. On the buying side, monopsony describes a single dominant buyer, most often discussed for labor markets. These models are the basis of antitrust analysis, merger reviews and the regulation of utilities and payment networks.
History and development
Many micro ideas date to Adam Smith's Wealth of Nations (1776), but the modern field took shape in the "marginal revolution" of the 1870s, when William Stanley Jevons, Carl Menger and Léon Walras independently argued that value depends on the usefulness of the last unit consumed. Alfred Marshall's Principles of Economics (1890) popularized supply-and-demand diagrams, and the twentieth century added general equilibrium theory, welfare economics and game theory, the last recognized in John Nash's 1994 Nobel prize. Later work added the economics of information (George Akerlof, Michael Spence and Joseph Stiglitz shared the 2001 prize) and behavioral economics, which uses psychology to explain systematic departures from purely rational choice. Since the 1990s the field has also become far more empirical, using household surveys, firm-level data and natural experiments; the 2021 prize went to David Card, Joshua Angrist and Guido Imbens for work of this kind.
Uses, criticism and limitations
Microeconomics is applied wherever a decision turns on prices and incentives: setting a tariff for an electricity network, judging whether a merger will raise prices, estimating who really bears a tax, or deciding how a bank should price a loan. Its strength is a consistent toolkit; its weakness is that the tidy models rely on simplifying assumptions. Critics argue that standard theory assumes too much rationality and information, gives too little weight to power, institutions and fairness, and treats market failures such as pollution as exceptions rather than common features. Supporters reply that the assumptions are starting points, and that much recent research, from behavioral studies to field experiments, exists precisely to test and relax them.