Stock market crash signals: which numbers warn before a fall?

Which signals give stock market crash warning signs?

A warning signal is a number that moves before prices do. Together 6 of them cover the main weak points of a market: borrowing costs, fear, price level, size against the economy, jobs, and structure. Each one rests on a public data series, so any reader can check it. Together they turn a vague worry into a short dashboard that you refresh each quarter.

A signal measures a condition, while a crash needs a trigger on top of that condition. History therefore shows signals flashing for months or years before a fall, and sometimes without any fall. The useful reading is a rising count of warnings, which lifts the probability of a crash and leaves the date open. Think of the dashboard as a weather map: it shows pressure building and supports preparation.

What does the yield curve say about stock market crash risk?

The yield curve compares what governments pay to borrow for short and long periods. Long rates normally sit above short rates. When short rates rise above long rates, the curve inverts, and bond investors are pricing slower growth ahead. Since 1970, every US recession came after an inversion of the 10-year minus 3-month spread, with leads between 6 and 17 months and an average of 12 months.

A recession weighs on company profits, so the curve works as an early and indirect crash signal. It moves slowly, which suits planning more than trading. The guide on yield curve inversion covers the two main spreads, the lead times, and the 2006-2007 episode that preceded the 2008 financial crisis. The gap between inversion and recession varies, so the signal sets a window rather than a date.

How does the VIX fear gauge read before a stock market crash?

The VIX measures the volatility implied by S&P 500 option prices over the next 30 days, which earns it the name fear gauge. Traders buy protection when they worry, option prices rise, and the index climbs. It reacts within hours, so it describes the present mood more than the distant future. On 16 March 2020 it closed at 82.69, the highest close since the index began in 1990.

A low reading shows calm, and calm can last for years before a shock. A high reading shows stress that has already arrived. The guide on the VIX index explains which levels deserve attention and how fear showed up in 1987, 2008, and 2020, so that you read the VIX as a thermometer and keep the forecasting job for slower signals.

Do CAPE and the Buffett indicator show a stock market crash coming?

CAPE divides a share index by the average of 10 years of inflation-adjusted earnings. The 20th-century average was 15.21. In 2014 Robert Shiller noted that readings above 25 had appeared in only 3 earlier periods since 1881, around 1929, 1999, and 2007. The Shiller CAPE ratio says how expensive a market is, and a high price level makes a fall larger when it comes.

The Buffett indicator divides the total value of listed companies by the size of the economy. Warren Buffett wrote in 2001 that a ratio near 200% meant playing with fire, while 70% to 80% favoured buyers. The guide on the Buffett indicator lists its limits, such as the overseas profits of multinational companies, so it reads best next to CAPE.

Which jobs and output data add to stock market crash warning signs?

Crashes and recessions often travel together, so jobs and output data add a second view. The Sahm rule flags a recession when the 3-month average unemployment rate rises 0.50 percentage point above its low of the previous 12 months. It uses one monthly series, which makes it fast and simple to follow. Economists have also questioned its reliability in the current economy.

The National Bureau of Economic Research dates recessions using employment, income, sales, and production, and it announces its decision months after the fact. The 2007-2009 recession ran from December 2007 to June 2009, which is 18 months. The page on recession indicators ranks these data by speed and by reliability, so you know which ones lead and which ones confirm.

What does the EQOS Asia score add to stock market crash signals?

The yield curve, the VIX, and valuation ratios each read one corner. The EQOS Asia φ(S) score reads the structure of the whole system across 9 dimensions, and a score under 0.3 marks the critical zone. According to the EQOS Asia study, the global financial system scored 0.234 in 2006-2007, with 6 of 9 dimensions critical (EQOS Asia 2008 back-test, 2026).

The same study put bank leverage at 30:1, so a fall of 3.3% in asset values was enough to bankrupt a bank, while the real fall in 2007-2008 reached about 20%. The EQOS score of a stock market applies that logic to current data, and anyone can recompute it from public inputs.

How do you read stock market crash signals together?

Start with the slow signals, the yield curve and valuations, to set the background. Add the VIX and recession data to see whether stress is arriving. Finish with the φ(S) score to see whether the structure can absorb a shock. When several signals warn in the same quarter, the probability of a fall rises and a review of position sizes becomes useful.

This page is general information, not investment advice. To run the structure test on your own exposure, the Λ simulator gives a first φ(S) estimate in minutes, and the EQOS Asia pricing page lists the full diagnostic for teams in Singapore, ASEAN, and Hong Kong.

Frequently asked questions

About the author

Stéphane Jambu

President, EQOS Forecast Asia

Stéphane Jambu leads EQOS Forecast Asia and works as a consultant in e-commerce, search visibility, and AI. LinkedIn profile