What is the output gap?

The output gap is the difference between an economy's actual output (real GDP) and its potential output, the level of GDP that would prevail if all resources (labor, capital, technology) were being used at their normal, sustainable rates. It is typically expressed as a percentage of potential GDP. A positive output gap means the economy is producing above its sustainable capacity; a negative gap means it is underperforming.

The output gap is a central concept in macroeconomic policy because it directly relates to inflation dynamics. When the economy runs above potential (positive output gap), labor markets are tight, capacity utilization is high, and firms face pricing power, all of which feed into inflationary pressure. When the economy runs below potential (negative output gap), slack exists in the form of unemployed workers and idle capacity, which puts downward pressure on inflation.

Potential GDP is not directly observable and must be estimated using models. The Congressional Budget Office (CBO) produces the most widely cited estimate, using a production function approach that combines trends in labor force growth, capital accumulation, and total factor productivity. Because potential GDP is estimated, the output gap inherits significant measurement uncertainty, particularly in real time when the data is still being revised.

The Fed uses the output gap (alongside related concepts like the unemployment gap and the Phillips curve) to calibrate its policy stance. When the output gap is significantly negative, the economy needs stimulus. When it is significantly positive, the Fed typically tightens to prevent overheating. The challenge is that potential GDP estimates are revised substantially over time, meaning the output gap the Fed is targeting in real time may look very different in hindsight.

For investors, the output gap provides a framework for understanding where the economy sits in the business cycle and what that implies for inflation, interest rates, and asset returns. A narrowing negative output gap suggests improving conditions and rising inflation, supporting cyclical assets. A widening positive output gap raises overheating risks and the probability of aggressive tightening, creating headwinds for rate-sensitive assets.