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The S&P 500’s October 12, 2022 closing low makes October 12, 2026 the four-year anniversary of the market’s climb from that bottom. Reuters reported the index was up 117% from the low as of October 9, 2026. The advance has been powered in part by AI investment and corporate earnings, but its reliance on a small group of companies leaves it exposed if expected profits fail to materialize. Four years is a milestone, not a countdown to an end.
What does the four-year anniversary measure?
The anniversary marks four years since the S&P 500’s closing low on October 12, 2022. Reuters’ October 9, 2026 report put the index near record levels and its cumulative rise at 117% from that low. That is a dated market snapshot, not a live return or a forecast.
Whether to call the entire period a “bull market” depends on the definition. A common convention is a 20% advance after a 20% decline, Reuters noted, but market experts do not use one universally agreed label. The more useful question is what has sustained the rise—and what could undermine it—not whether a rally is too old to continue.
What has driven the rally?
AI investment and corporate earnings
Reuters’ anniversary report identified AI-related capital spending, corporate profits and a solid economic backdrop as important supports. Large technology companies’ spending on data centers has created demand for chips and related equipment while helping drive investment across the economy.
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Reuters reported that S&P 500 earnings were expected to grow more than 35% in 2026, with data-center investment by major cloud and technology companies cited as a driver. That figure is an estimate, not a final result for the year. The distinction matters: current earnings and spending are observable, while the eventual profits from AI adoption remain uncertain.
Gains have not been evenly spread across sectors
In Reuters’ account of the bull-market period, information technology and communication services were the only S&P 500 sectors to outperform the index. The Federal Reserve’s July 2026 Monetary Policy Report said the S&P 500 had risen about 9% since the start of 2026 and the information technology industry group about 16% through the report’s measurement period. It also noted sizable market fluctuations in response to AI developments and geopolitical events. These are period-specific figures, not current readings beyond the report’s cutoff.
How much does the market depend on a few companies?
In a capitalization-weighted index such as the S&P 500, larger companies have more influence on the index’s result. Reuters cited J.P. Morgan Asset Management’s estimate that the ten largest constituents together made up about 40% of the index in its October 2026 snapshot, compared with about 28% in October 2022. A strong performance by a few giants can lift the headline index; weakness in the same names can weigh on it disproportionately.
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Concentration is a vulnerability, not proof that a decline is imminent. As Edward Jones strategist Angelo Kourkafas put it in Reuters’ October 9 report: “The risk of concentration is that if the prevailing theme goes out of favor, portfolios might feel it in an outsized way.” If investors mark down a handful of major AI-exposed companies, their large index weights can transmit that weakness to the broader benchmark.
What could put pressure on stocks?
AI spending may not produce the expected returns
Capital spending can raise demand and support suppliers before its long-term payoff is clear. Federal Reserve Governor Michael Barr said in a September 29, 2026 speech that AI investment was boosting business fixed investment and demand for chips and related equipment. He also stressed that the productivity payoff’s timing is uncertain: companies may need to reorganize how work is done to benefit from new technology. As Barr put it, “A key question for monetary policy, both in the near term and for years to come, will be the effect of AI on the productive capacity of the economy and the structure of the labor market.”
The uncertainty is not only whether AI will improve productivity, but who will capture the value. Companies investing heavily may face competition, costly build-outs or customers unwilling to pay enough to justify the expense. Vanguard’s 2026 outlook described both sides: faster AI adoption and investment could support growth and earnings, while weak returns on expensive investment could disappoint. Its projections were forecasts made for that outlook, not realized performance or personalized advice.
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Valuations, yields and monetary policy can change the equation
Federal Reserve Vice Chair Philip Jefferson’s November 2025 speech drew a distinction between many current AI-linked companies, which generally have established and growing earnings, and many dot-com-era firms whose earnings were limited and revenue prospects speculative. That difference is relevant, but it does not prove current stock prices are justified: rapid price gains and uncertain expectations still matter.
Higher Treasury yields can make bonds more competitive with stocks and put pressure on equity valuations, particularly when prices depend on profits expected far in the future. Reuters reported the 10-year Treasury yield was around 5.2% on October 9, 2026, after a recent 24-year high. That is a dated snapshot, not a current yield or a mechanical signal that a bull market is ending.
Inflation and monetary policy are part of that backdrop. The Federal Reserve’s July 2026 Monetary Policy Report recorded PCE inflation of 4.1% and core PCE inflation of 3.4% over the 12 months through May 2026. Those are the report’s stated readings for that period; they should not be mistaken for later inflation data. The course of inflation and interest rates can affect financing costs, bond yields and the valuations investors are willing to pay.
A market decline could affect household spending
A large stock-market fall would matter beyond investors’ account balances. Atlanta Fed researchers modeled hypothetical S&P 500 declines of 25%, 35% and 50% and projected lower U.S. real consumption through the equity-wealth effect: households that feel less wealthy may reduce spending. Those percentages are scenario inputs, not predictions that a decline will happen or estimates of a certain future outcome.
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Does a four-year bull market have to end?
No. The anniversary alone says little about what comes next. Reuters quoted Nationwide strategist Mark Hackett saying, “Four years is not, by any stretch of the imagination, scary with regards to a bull market,” and “They don’t end of old age; they end from disease.” His wording is a market strategist’s view, not a law or a consensus forecast.
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The practical risks are the conditions behind the metaphor: a sharp deterioration in earnings, disappointment over AI returns, higher yields or tighter financial conditions, or a selloff among heavily weighted companies. Reuters also quoted Ameriprise strategist Anthony Saglimbene: “The AI theme is the defining feature of this bull market.” He said investors were past the easiest gains from the theme and that technology companies faced more pressure to show that current spending turns into profits. Those are concerns to monitor, not a timetable for a reversal.
What should readers take from the anniversary?
The rally has real supports—earnings, substantial AI-related investment and a wider economic backdrop—but the benefits and risks are unevenly distributed. The index’s concentration makes the performance of a small set of large firms especially consequential, while the payoff from AI investment is still being worked out. The anniversary is best read as a checkpoint: the market has risen sharply, but its next direction will depend on earnings, valuations, interest rates and whether AI spending ultimately earns adequate returns.
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