Recessions: Definition, Causes, and Market Behaviour

Technical Definition

Two consecutive quarters of falling real (inflation-adjusted) GDP is the rule of thumb you will see most often in the news, and the UK's statistics office uses it. The NBER, which dates US recessions, uses a broader lens:

• Real GDP and income decline (income excluding government transfer payments)
• Employment falls (payrolls shrink, jobless claims rise)
• Real spending and sales fall
• Industrial production contracts
• The fall must be deep, widespread and lasting; there is no fixed minimum length

Why the broader approach? The 2020 COVID recession lasted only two months (February to April 2020) but was the deepest since the 1930s. Looking at jobs and income captures shocks like that better than quarterly GDP. The trade-off is speed: the NBER usually announces a recession many months after it has begun, and sometimes after it has already ended.

Severity Spectrum

Mild recession (GDP falls 1–2%): unemployment rises 1–2 percentage points. Example: 1990–91, when US GDP fell about 1.4% and the S&P 500 fell about 20%. The 2001 recession was milder still in GDP terms, yet shares fell almost 50% from 2000 to 2002 as the dot-com bubble deflated: the size of a market fall and the depth of a recession are not the same thing.

Severe recession (GDP falls 3–5%): unemployment rises 3–5 points. Example: 2007–09, when US GDP fell about 4%, unemployment peaked at 10% and the S&P 500 fell 57%.

Depression (a fall far deeper and longer than a normal recession): Example: 1929–33, when US GDP fell by about a quarter and prices fell too. Central banks and governments now respond much faster, which is one reason no developed economy has had a depression on that scale since.

The Fed Tightening Cycle (Most Common)

Mechanism: Inflation rises → Fed raises rates aggressively → borrowing costs spike → companies cut capex, consumers reduce spending → demand falls → unemployment rises → recession.

Examples: 1980 and 1981–82 (Paul Volcker's Fed raised rates to nearly 20% to break inflation), 1990–91 (rate rises plus an oil price spike), 2001 (rate rises in 1999–2000 as the dot-com bubble burst).

Supply Shocks

A sudden jump in costs, such as an oil embargo, can push inflation up while growth slows, a mix called stagflation. Central banks then face a hard choice: raise rates and deepen the slowdown, or hold back and risk inflation becoming entrenched. Example: the 1973 oil embargo quadrupled oil prices and was followed by the 1973–75 recession. After a second oil shock in 1979, the Fed chose to tighten hard, which led to the recessions of the early 1980s.

Financial Crises

Bank failures, credit markets seizing up, or a bubble bursting can cut off lending quickly. Example: losses on US subprime mortgages → banks short of capital → lending freezes after Lehman Brothers fails in 2008 → the Great Recession.

Demand Destruction

A sudden event can stop spending outright. Example: the 2020 pandemic. Lockdowns shut large parts of the economy; the S&P 500 fell 34% in about a month, then recovered quickly as governments and central banks provided very large support.

Yield Curve Inversion

Short-term yields above long-term yields. The curve inverted before every US recession since 1969, typically 6–24 months ahead, but it also inverted from 2022 to 2024 without a recession following.

Unemployment Rise +0.5%

The Sahm Rule, named after economist Claudia Sahm: when the 3-month average unemployment rate rises 0.5 points or more above its low of the previous 12 months, a recession has usually already begun. It caught every US recession since 1970, but it triggered in August 2024 without one, partly because more people were joining the labour force.

LEI (Leading Economic Index)

The Conference Board's composite of 10 forward-looking indicators (jobless claims, new orders, hours worked and others). A sustained, broad decline has historically come before recessions. It fell for about two years from 2022 without one, so it is most useful alongside other signals.

Profit Margin Compression

When input costs rise (wages, commodities) faster than companies can raise prices, margins fall. Companies respond by cutting investment and hiring, which slows the economy further. Falling margins have often shown up in company results before the economy-wide data turns.

Before a Recession

When the yield curve inverts or leading indicators decline, long-dated bonds and defensive sectors (utilities, staples, healthcare) have historically held up better than cyclicals such as materials, industrials and energy.

During Recession

Shares usually fall: the S&P 500 dropped 49% from 2000 to 2002, 57% from 2007 to 2009, and 34% in 2020. High-quality government bonds have often risen as central banks cut rates, as in 2001 and 2008. That is not guaranteed: in the inflationary recessions of the 1970s, bonds fell too.

Recovery Window

An important pattern: share prices have tended to bottom several months before a recession ends. On 9 March 2009 the S&P 500 closed at 677, 57% below its 2007 peak. The recession ended in June 2009, but the NBER did not announce that until September 2010, by which time the S&P 500 was more than 60% above its low.

Case Study: 2007–09

Long-dated US Treasuries rose through the downturn as the Fed cut rates to near zero. The S&P 500 did not regain its October 2007 peak until March 2013, five and a half years later.