Bank of America Issues Rare Contrarian Sell Warning as AI Stock Concentration Soars

TLDR

• Bank of America’s Bull & Bear Indicator reached 8.0, activating a contrarian sell alert for risky investments.
• Strategist Michael Hartnett cautioned that AI companies could represent 47–48% of total U.S. equity market value, exceeding dot-com era peaks.
• Technology stocks saw their strongest hedge fund buying activity in almost three months, according to Goldman Sachs data.
• Increasing bond yields and inflationary pressures pose the greatest risks to the current AI-driven market surge.
• Cryptocurrency bitcoin has declined over 11% year-to-date while crude oil has surged more than 70%, highlighting divergent asset class trends.

Michael Hartnett, chief investment strategist at Bank of America, delivered a cautionary message this week regarding the U.S. equity market’s intense focus on artificial intelligence, suggesting it may be reaching levels of speculation comparable to some of the most notorious financial manias in history.

In his May 22 client note, Hartnett projected that if expected blockbuster public offerings from firms including SpaceX, OpenAI, and Anthropic come to fruition, the artificial intelligence sector could command between 47% and 48% of total U.S. stock market value. This concentration would eclipse what was witnessed during the late-1990s internet bubble, Japan’s asset boom of the 1980s, and the Nifty Fifty phenomenon, trailing only the railroad mania of the 1880s.

Hartnett identified robust upward price trends, declining market volatility, and significant retail trading activity as indicators that speculative excess is already embedded in today’s markets.

Contrarian Sell Warning Activated

The Bull & Bear Indicator maintained by Bank of America climbed to 8.0, activating what the bank characterizes as a contrarian sell warning. This proprietary gauge monitors investor sentiment and market positioning, with readings exceeding 8 historically foreshadowing softer market performance.

Hartnett observed that since 2002, there have been 17 instances when this sell signal was triggered. Following these alerts, international equities typically declined between 2% and 3% over the subsequent two to three months, with peak losses sometimes reaching 15% to 20%.

Yet money continues flowing into markets. U.S.-focused equity funds recorded their eighth consecutive week of inflows. Technology-sector funds alone attracted $9 billion, marking the most significant weekly influx since October 2025.

Private wealth clients of Bank of America now maintain an unprecedented 65.7% allocation to stocks. Meanwhile, cash holdings have dropped to approximately 10%, approaching all-time lows.

Hartnett identified climbing bond yields as the primary danger confronting the current rally. He cautioned that “bond vigilantes” are beginning to resist prevailing market enthusiasm, with vulnerabilities emerging across emerging markets, residential real estate, and private equity sectors.

He highlighted weakness in Asian currencies including the Indian rupee and Indonesian rupiah as evidence of mounting financial strain. Additionally, he noted a dramatic increase in semiconductor pricing across Asia, with Korean semiconductor export values climbing 148% year-over-year and DRAM chip prices surging 223%, contending that Asian markets are transmitting inflationary pressure globally.

Institutional Investors Double Down on Technology

Meanwhile, a separate client communication from Goldman Sachs released Friday revealed that hedge funds accumulated technology equities last week at the most aggressive rate witnessed in nearly three months.

Purchasing activity was most pronounced in North American and emerging Asian markets measured by dollar volume. Fund managers favored semiconductor manufacturers and software developers while reducing exposure to communications infrastructure and IT consulting firms.

Hedge fund positioning in technology stocks relative to the MSCI World Index has reached its most elevated level in more than five years. Exposure to global information technology equities now stands at record highs based on Goldman Sachs Prime Brokerage tracking data extending back to 2016.

Goldman observed that artificial intelligence-focused enterprises, especially semiconductor and chip producers, have demonstrated resilience despite worldwide economic volatility related to the Iran conflict.

Divergent Performance Across Investment Categories

Oil has emerged as the strongest-performing major asset class in 2026, climbing more than 70% since January. Emerging-market stocks have advanced over 17%. Bitcoin has retreated more than 11% during the same period.

Hartnett maintained that commodities and developing-market equities represent compelling long-term investment themes. He also proposed that consumer-focused stocks could present attractive opportunities once the present market cycle reaches its zenith.

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