Overheating (Economy)

Overheating describes an economy in which spending grows faster than the economy's capacity to produce for a sustained period. Firms run short of workers and materials, wages and prices rise quickly, and inflation climbs above the central bank's target. Overheating is the late-expansion phase of the business cycle taken too far.

Economists usually describe overheating as a positive output gap, meaning actual output above its sustainable or "potential" level, combined with unemployment below its natural rate. It is the opposite of slack. Central banks, finance ministries and bodies such as the IMF and OECD watch for it because an overheated economy is prone to a sharp correction, sometimes a boom and bust.

Think of a car engine pushed hard up a long hill. For a while it delivers more power than usual, but run it in the red zone too long and it overheats, parts wear out and something eventually breaks. The fix is to ease off the accelerator before the damage is done.

An economy works in a similar way. It can grow faster than normal for a while by using spare workers and factories. Once those run out, extra demand mostly pushes up prices and pay rather than producing more. Policymakers then try to cool things down, usually by making borrowing more expensive.

The output gap is the standard summary measure of overheating:

• $Y$ is actual real output, usually real GDP.
• $Y^{*}$ is potential output, the level the economy could sustain without rising inflation.

If real GDP is 2,040 and estimated potential output is 2,000, the gap is $(2{,}040 - 2{,}000) \div 2{,}000 \times 100 = +2\%$: the economy is running 2% above capacity. Potential output cannot be observed directly, so estimates differ between institutions and are often revised heavily years later, which makes real-time judgements of overheating uncertain. The US Congressional Budget Office, the IMF, the OECD and national central banks all publish their own estimates of potential output, using methods that range from simple statistical trends to production-function models built from labour, capital and productivity. They can disagree by a percentage point or more, enough to turn an apparently overheated economy into one with spare capacity.

Because the output gap is hard to pin down, analysts look at a range of symptoms together:

• A tight labour market. Unemployment below estimates of the NAIRU, many unfilled job vacancies and rapid wage growth, the trade-off described by the Phillips curve.
• Rising core inflation. Price increases spreading beyond volatile food and energy into services, with a risk of a wage-price spiral.
• Capacity strains. High factory utilization, long delivery times and shortages of materials.
• Credit and asset prices. Fast credit growth, soaring property and share prices, and sometimes an economic bubble.
• External imbalances. In open and emerging markets, a widening current account deficit as demand spills into imports, often financed by short-term capital inflows.

In the United States in the late 1960s, war spending and expanded social programmes pushed unemployment below 4% and set off the rise in inflation that ran into the 1970s. Britain's "Lawson boom" of the late 1980s, fuelled by tax cuts and a credit and housing surge, saw inflation return to double digits by 1990 before a recession. After the pandemic, strong fiscal support, pent-up demand and supply bottlenecks combined in 2021–2022; US consumer price inflation peaked at 9.1% in June 2022, measured by the consumer price index, and many advanced economies saw similar surges. Economists still debate how much of that episode reflected overheating demand and how much reflected supply shocks such as energy prices after Russia's invasion of Ukraine.

The main tool is tighter monetary policy: central banks raise interest rates, as guided by frameworks such as the Taylor rule, and may shrink their balance sheets through quantitative tightening. Governments can help by tightening fiscal policy, raising taxes or slowing spending, though this is politically harder. Regulators may also cap mortgage lending or raise bank capital buffers. The challenge is timing: policy acts with long lags, so tightening too late lets inflation become entrenched, while tightening too hard can tip the economy into recession. A "soft landing", in which inflation falls without a downturn, is the goal but has historically been difficult to achieve.

• Federal Reserve Board: Federal Open Market Committee
• US Bureau of Economic Analysis: Gross Domestic Product