Output gap

Every economy has a maximum sustainable level of output — the amount it can produce when all workers who want a job have one and all factories are running at normal capacity. When the economy is running above that level (a positive output gap), workers are scarce, wages rise, and businesses can charge more — creating inflationary pressure. When it is running below (a negative output gap), workers are idle, wages stagnate, and firms discount prices to win customers — creating disinflationary or deflationary pressure.

The output gap is therefore one of the fundamental drivers of inflation over the medium term. It is why central banks care about GDP growth, unemployment, and capacity utilisation — not just the price index itself. The IMF and OECD both publish output gap estimates for use in monetary policy analysis.

Potential output is not observable — it must be estimated. The most common approaches are: (1) statistical filters that smooth the actual GDP series to extract a trend; (2) production function approaches that model potential output from capital, labour, and total factor productivity; and (3) multivariate methods that use unemployment and inflation data alongside GDP. Each gives a different answer, and output gap estimates are frequently revised. The CBO publishes US estimates quarterly; the OECD covers all 38 member countries.

The output gap is central to understanding the 2021–2022 inflation surge. Massive fiscal stimulus in the US and Europe, combined with supply constraints, created a large positive output gap — the economy was trying to spend more than it could produce. This excess demand was the fundamental cause of inflation, alongside supply-side factors. The IMF World Economic Outlook uses output gap estimates to project inflation for 190 countries. The ECB's Economic Bulletin publishes euro-area output gap assessments alongside its quarterly inflation projections.

Output gap estimates are highly uncertain and frequently revised — sometimes by several percentage points. The IMF and OECD regularly revise their historical output gap estimates as better data arrives. This uncertainty matters because policy errors can be large: the 2021 consensus that US output was not overheating was proven wrong in hindsight. A negative output gap does not guarantee disinflation — if inflation expectations are de-anchored or supply-side factors are dominant, the gap-inflation relationship can break down, as the 1970s stagflation demonstrated.