In plain terms — The business cycle describes acceleration and deceleration in activity. The output gap compares measured output with an estimated potential level.
Expansion, slowdown, recession and recovery read through coincident and leading evidence without treating the output gap as an observable fact.
What it actually observes
The business cycle is the irregular sequence of expansion, slowdown, recession and recovery. The output gap compares actual production with estimated potential; a negative gap signals spare capacity, not necessarily an economy that is currently contracting.
Output, income, employment and sales do not turn on the same day. Official recession dates are often established months later and cannot be used as if they were a real-time signal.
Operational reading
A useful diagnosis separates level from impulse. An economy can continue growing while losing momentum, so leading, coincident and lagging evidence must be ordered by the date it was genuinely available.
Seek confirmation across final demand, inventories, hours, credit and investment. A classification that depends on one volatile series remains a hypothesis rather than a measured regime.
Worked interpretation
A negative output gap that is closing indicates movement toward potential, not necessarily a strong expansion.
Advanced level
Potential output depends on capital, labour and productivity and is estimated with models that are revised. Two-sided filters that use future data can make past turning points look artificially clear.
Tests of cyclical strategies need one-sided estimates or historical vintages, explicit decision dates and costs. Regime probabilities are more honest than a hard boundary when indicators disagree.
Limits and common errors
Neither the cycle nor the output gap is directly observable or mechanically periodic. Sector shocks, structural change and revisions can move turning points, and a statistical recession label is not by itself a market forecast.
Sources
- NBER, Business Cycle Dating, official documentation — criteria and chronology used to date U.S. expansions and recessions.
- CBO, Budget and Economic Data, official documentation — historical and projected potential output, GDP and output-gap series.
- OECD, Composite Leading Indicator, official documentation — a composite indicator designed to signal turning points in economic activity.