Soaring price-to-sales and market-cap-to-GDP readings, large moves in the market value of multi-trillion-dollar companies and periodic, sharp selloffs have amplified concerns that parts of the U.S. equity market could be exhibiting bubble-like characteristics. Skepticism has centered on the dramatic gains among artificial intelligence-related and semiconductor companies, with investors questioning whether the rally has taken on speculative traits.
Those anxieties intensified last week after technology shares registered a pronounced decline, a pullback that market participants attributed to worries about debt-funded AI investments and concern that the Federal Reserve might tighten policy more than expected. Since then, equities have shown signs of stability as many investors point to improving sentiment, a broadening of market leadership and steady corporate earnings as supporting factors for continued gains - but unease persists among some strategists.
Market fragility indicators climb
"Looking through the lens of valuations, positioning, and sentiment ... all measures of asymmetry and risk are flashing amber," said Oliver Shale, investment specialist for the U.S. at Britain-based Ruffer. Several valuation gauges have risen toward near-record heights, and particular sentiment metrics are running at elevated levels.
Bank of America Global Research’s proprietary Bubble Risk Indicator, which scores asset price behavior on a scale from 0 to 1 with 1 denoting extreme bubble-like action, was registering readings of 0.91 for the PHLX Semiconductor Sector and 0.82 for the Technology Select Sector. Those scores underscore how stretched prices are in those areas relative to historical norms.
Valuation measures flag worry
One widely watched broad-market measure, the Buffett Indicator - which compares total U.S. stock market capitalization to gross domestic product - stood at 218% in the first quarter, marginally below the record 219% reached in the prior quarter. That elevated ratio is consistent with historical levels associated with major market downturns.
The S&P 500 price-to-sales ratio is currently at 3.22, according to Tajinder Dhillon, head of earnings research at LSEG. That compares with its long-term historical average of 1.84, signaling that market valuations are extended on a sales basis. "Nearly every S&P 500 valuation metric is higher than it’s ever been except, possibly, PE ratios," said Mark Spiegel, managing member and portfolio manager at Stanphyl Capital Partners.
While the S&P 500 price-to-earnings ratio has not yet matched the extremes seen in prior market bubbles - in part because earnings have been robust - doubts remain about the sustainability of those earnings. Spiegel noted there is a case to be made that the "E" in valuation ratios could itself be forming an unsustainable bubble.
The S&P 500’s price-to-earnings ratio stands at 20.2 times expected 12-month earnings, compared with 25.2 during the dotcom episode, based on LSEG Datastream data cited by market analysts. The recent surge in demand for AI-driven chips has created substantial winners among equipment and component suppliers, yet questions persist about whether firms that are directing large capital outlays toward AI will realize commensurate returns. "The folks selling the picks and shovels are in incredibly good stead. Those buying them still have to prove that the billions and billions of dollars they’re spending is worth it," said JJ Kinahan, head of retail expansion and alternative investment products at Cboe Global Markets.
Sentiment and positioning show mixed signals
Measures of investor sentiment and market positioning are less uniform. Bank of America’s June global fund manager survey indicated that investors remained broadly bullish, though sentiment eased slightly from May. In the American Association of Individual Investors (AAII) Sentiment Survey, bearish sentiment declined markedly while bullish views rose, pushing the bull-bear spread to 8.8% - above its historical average of 6.5% and marking only the second time in 20 weeks that it has exceeded that mean. The current spread remains well below its 44.2% peak, which suggests there are not widespread signs of outright euphoria.
Some observers have pointed to a healthier distribution of gains across sectors as a constructive sign. After widening to roughly a 14 percentage-point gap in early 2026, the performance difference between the S&P 500 and its equal-weighted counterpart has narrowed in recent sessions to about 3 points, which market watchers interpret as meaningful broadening of the advance.
"A red flag is when sentiment and positioning is at extremes, and that’s not what we see now," said Angelo Kourkafas, senior global investment strategist at Edward Jones.
Practical caution advised
Even as the market has shown resilience, some strategists advise prudence. "It does look like too many people are assuming fat margins and high growth rates are here to stay, while I’m a bit more skeptical about that outlook," said Brian Jacobsen, chief economic strategist at Annex Wealth Management. Diversification, he and others suggest, is a sensible approach given the mix of stretched valuations and lingering uncertainties.
In short, while recent broadening of participation, solid earnings flows and easing sentiment pressures have helped steady markets after the tech pullback, a range of valuation and positioning indicators remain at levels that some investors view as fragile. That combination - high prices in a handful of sectors, large swings in the market values of major companies and ongoing questions about the returns on heavy AI-related spending - keeps debate alive over whether elements of the market are in a bubble.