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Bull or bear market? AI spurs rethink of traditional market measures

Published by Global Banking & Finance Review

Posted on September 2, 2026

4 min read

· Last updated: September 2, 2026

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Is It a Bull or Bear Market? AI Redefines Traditional Measures for Investors

Rethinking Market Labels in the Age of Volatility and AI

By Johann M Cherian and Niket Nishant

The Challenge of Defining Bull and Bear Markets

Sept 2 (Reuters) - Everyone knows Wall Street calls a 20% drop in a major index a bear market. But what do you call it when the index posts big gains and losses practically every day and is still way up for the year?

That question is testing the limits of the market's most familiar vocabulary and prompting some to question whether a term like bear market really applies when tech indexes are red hot and constantly gyrating.

Expert Opinions on Market Volatility

"It's kind of lazy nomenclature to be using on things that are that volatile," said Art Hogan, chief market strategist at B. Riley Wealth.

The Philadelphia SE Semiconductor Index, a benchmark for chip stocks, and South Korea's tech-heavy KOSPI both entered bear markets in July, based on the traditional measure. But even at their troughs, the indexes were still up 46% and 25%, respectively, for the year, thanks to triple-digit percentage gains over the past year.

If that's a bear, it's not a particularly unfriendly one at the very least.

"These labels that people use probably make some sense for broad markets, but not for indexes such as SOX and KOSPI, which have had crazy parabolic runs," said Steve Sosnick, chief strategist at Interactive Brokers.

The Impact of Labels on Investor Perception

While the debate may seem academic to some, the labels shape how investors perceive the severity of selloffs, and in the past have served as important markers to distinguish between routine pullbacks and a long-term shift in fundamentals.

A bear market can last for months. Since 1928, bear markets in the S&P 500 have on average lasted 289 days, or about 9.6 months, according to data from Hartford Funds.

What's a Better Measure?

The debate on what constitutes a bear market is hardly new. In a 2008 blog post, Barry Ritholtz, co-founder and chief investment officer of Ritholtz Wealth Management, urged investors to ignore the "squishy terminology."

But what seems like a semantic distinction can carry real investment consequences.

The Risks of Relying on Traditional Labels

Given the potential boost from the AI boom, investors risk missing out on gains if traditional labels give them a false signal to sell. Indeed, the SOX and KOSPI have rebounded since their trip into old-fashioned bear territory, meaning investors who sold at the bottom would have missed out on recent gains.

Earnings for the S&P 500 semiconductors and equipment industry group are estimated to grow at least 114.7% this year, LSEG-compiled data showed.

Toward a New Definition of Bear Markets

There is no consensus on what should replace the traditional definition of bear markets. But among more than a dozen analysts Reuters interviewed, some argue that any new measure should account for the length of the decline, the underlying volatility, the broader direction of the economy and other factors.

Expert Criteria for Redefining Bear Markets

"A bear market needs to be sustained over multiple weeks or months for confirmation. Deeper structural forces in the market need to be negative for a bear market to be real, such as high interest rates and peaking of the economy," said David Russell, global head of market strategy at TradeStation.

Moving averages, which track the average price movement over a period, and Fibonacci retracement, used to identify potential levels where a stock's decline may slow or reverse, could also be used to guide positioning, other investors said.

Interactive Brokers' Sosnick said that a decline must at least exceed the index's one-year historical volatility on an annualized basis to be considered a bear market. By those measures, the SOX would need to fall more than 44% to qualify as a bear market, he said.

The Future of Market Definitions

While a new definition could possibly better reflect the volatile nature of the SOX, KOSPI and Wall Street's tech-elite Nasdaq 100 indexes, it is likely to be less tidy than the current measure.

That may leave investors relying more on experience than any fixed threshold.

"For us guys that have been around a long time, it's more of a 'feel' type situation," said Joe Saluzzi, co-head of equity trading at Themis Trading.

(Reporting by Johann M Cherian and Niket Nishant in Bengaluru, editing by Colin Barr and Sriraj Kalluvila)

Key Takeaways

  • Traditional bear market defined as a 20%+ drop is outdated for highly volatile, tech‑heavy indexes driven by AI‑powered rallies (e.g., SOX and KOSPI remain up 25‑46% YTD despite entering bear territory) (axios.com).
  • Historical data show S&P 500 bear markets average ~289 days (~9.6 months), emphasizing their depth and duration—not mirrored by fast, volatile tech declines amid AI boom (hartfordfunds.com).
  • Analysts advocate for refreshed metrics—factoring in sustained duration, structural economic indicators, volatility thresholds, moving averages or Fibonacci retracements—to better capture market dynamics under modern conditions (ubs.com).

References

Frequently Asked Questions

What is the traditional definition of a bear market?
A bear market is typically defined as a 20% drop in a major index from recent highs, lasting on average about 9.6 months.
How has AI-driven volatility impacted traditional market labels?
AI-driven gains and daily swings in tech indexes challenge traditional terms like 'bear market,' making them less relevant in volatile, high-growth environments.
Why do some experts question the current bear market definition?
Experts argue that with indexes like SOX and KOSPI posting massive yearly gains despite large swings, traditional definitions may mislead investors.
What alternative measures for defining bear markets are suggested?
Analysts suggest measures based on decline length, historical volatility, economic conditions, moving averages, and Fibonacci retracement.
What are the risks of relying solely on traditional market terminology?
Using old labels may cause investors to miss gains during rebounds or misjudge the severity of market corrections driven by factors like AI.

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