A business cycle is a broad fluctuation in aggregate economic activity, conventionally described as alternating expansions and contractions separated by peaks and troughs. The word cycle can mislead: these movements recur, but they do not follow a fixed timetable, and neither phase has a predetermined duration. The central issue is whether economic activity is rising or falling broadly across the economy, not whether a calendar pattern says a turn is “due.”
Direction is not level
A peak marks the transition from expansion to contraction; a trough marks the transition from contraction to expansion. That does not mean the economy is strong at a peak or healthy immediately after a trough. An expansion describes a period in which aggregate activity is rising, so output, income or employment can remain below a previous peak for part of the expansion. Likewise, individual sectors and indicators do not have to turn at the same moment. A business-cycle phase is therefore an aggregate judgment, not a claim that every industry, region or data series is moving together.
Dating the cycle
There is no universal mechanical rule that turns one data release into a business-cycle turning point. In the United States, the National Bureau of Economic Research dates peaks and troughs using a range of economy-wide indicators and considers the depth, diffusion and duration of a decline rather than applying a fixed formula. Its procedure is not the same as the common shorthand of “two consecutive quarters of falling real GDP,” and its turning-point calls are intentionally retrospective because the committee waits for enough evidence and allows time for data revisions.
For practitioners, that timing distinction matters. Business-cycle dating is most useful as a framework for organizing macroeconomic conditions and comparing how growth, employment, income, production and markets behave across expansions and contractions; it is not designed to be a real-time trading signal. A formal recession call can arrive after the peak it dates. Business Cycle should also be kept separate from Seasonality, which concerns recurring calendar-linked patterns, and from Commodity Cycle, which can reflect sector-specific supply, demand and investment dynamics even when the broader economy is in a different phase.