Economics is a social science concerned with the production, distribution, and consumption of goods and services and the allocation of scarce resources among competing uses. It examines how individuals, businesses, and governments make decisions, respond to incentives, and interact through institutions. Its subject matter extends beyond money and finance to questions of work, inequality, environmental protection, and collective decision-making. Economists use theoretical models and empirical evidence to explain economic outcomes and evaluate alternative arrangements and policies. (aeaweb.org)
Scarcity, choice, and coordination
Scarcity means that available resources—including time, labor, land, and equipment—cannot satisfy every possible use. Choices therefore involve trade-offs. The opportunity cost of an action is the value of the best alternative forgone, rather than simply its monetary expense. Studying, for example, may involve both tuition payments and earnings sacrificed by not working. Marginal analysis examines the additional benefits and costs of a small change, such as producing one more unit or working another hour. (openstax.org)
Economic analysis distinguishes productive efficiency, in which producing more of one output requires sacrificing another, from allocative efficiency, which concerns the composition of output relative to people's preferences. Comparative advantage explains how specialization according to relative opportunity costs can increase total production through trade, even when one producer is more productive in every activity. These concepts describe possibilities for gains; they do not by themselves establish how those gains will be distributed. (openstax.org)
Economic coordination takes place through several arrangements. A market connects buyers and sellers, with prices conveying information and influencing behavior. Firms coordinate activities internally, while public authorities, households, and communities also allocate resources through rules, planning, cooperation, and sharing. Economics investigates how these arrangements operate and how their institutional setting affects outcomes. (books.core-econ.org)
Microeconomics and macroeconomics
Microeconomics studies individual decision-makers and their interactions. Its subjects include consumer choices, business production, wages, competition, and the functioning of particular markets. Supply and demand provides a basic framework for examining prices and quantities. More elaborate models incorporate monopoly power, imperfect information, and interactions among multiple markets. Microeconomic analysis also examines how taxes, regulations, and other interventions affect behavior and welfare. (imf.org)
Macroeconomics studies economy-wide outcomes, including employment, inflation, national income, and economic growth. It considers how consumption, investment, and other aggregate activities interact, and how government spending, taxation, and monetary policy influence economic fluctuations. The distinction is analytical rather than geographical: an individual market may span many countries, while macroeconomic research may investigate a single national economy. (imf.org)
Gross domestic product is a widely used measure of economic output, but output is not identical to well-being. Distribution, leisure, unpaid activities, and environmental conditions also matter when assessing living standards. The distinction between economic quantities and broader welfare is important when comparing societies or evaluating changes over time. (books.core-econ.org)
Historical development
Economic inquiry predates economics as a distinct academic discipline. Modern economics developed from political economy, which investigated production, commerce, public revenue, and the distribution of wealth. Adam Smith's The Wealth of Nations, published in 1776, examined specialization and the coordination of decentralized economic activity. His work appeared during the early Industrial Revolution, when changes in production and commerce were transforming economic life. (imf.org)
The Great Depression intensified research into economy-wide instability. John Maynard Keynes's The General Theory of Employment, Interest and Money (1936) helped establish macroeconomics as a distinct field by examining relationships among aggregate output, employment, and expenditure. Later research increasingly connected aggregate models with the decisions of individual households and firms. (imf.org)
Models and empirical methods
Economic models simplify reality to isolate relationships and mechanisms. Their assumptions specify the actors, constraints, information, and rules relevant to a question. Models may be expressed verbally, graphically, or through mathematics. Their usefulness depends on whether the simplifications clarify the phenomenon being studied, not on reproducing every detail of an economy. (imf.org)
Econometrics combines economic reasoning with statistical methods to investigate data. A central difficulty is distinguishing correlation from causation: people exposed to different conditions may also differ in other consequential ways. Researchers use approaches including randomized controlled trials and natural experiments to identify causal effects. Natural experiments exploit circumstances, such as policy changes or eligibility rules, that generate informative comparisons without researchers directly assigning treatment. Their interpretation still requires explicit assumptions about comparability and participation. (nobelprize.org)
Institutions, behavior, and policy
Economics also investigates departures from idealized market outcomes. Externalities arise when an activity imposes costs or benefits on others that are not fully reflected in its price. Pollution, for example, can create a gap between private production costs and social costs. Such differences help explain why decentralized decisions may produce socially inefficient quantities. (imf.org)
Behavioral economics examines how psychological processes and experience shape decisions, including departures from conventional assumptions of consistently optimizing behavior. This research expands the analysis of choices by studying how people perceive information, form expectations, and respond to circumstances. (imf.org)
A further distinction separates positive analysis—claims about what happens or would happen—from normative analysis—judgments about what ought to happen. Evidence can inform policy comparisons, but choosing among outcomes also requires judgments about fairness, rights, and acceptable trade-offs. Economics therefore distinguishes explanations of behavior from the value criteria used to assess it. (openstax.org)