Wall Street’s AI bubble warning: Bank of America says the combined listings of SpaceX, OpenAI, and Anthropic will push tech’s share of the S&P 500 past a threshold not seen since the Roaring Twenties

Wall Street analysts are sounding alarms over escalating concentration in technology stocks. Bank of America strategist Michael Hartnett has highlighted how anticipated public listings of major private companies could drive the sector’s weight in the S&P 500 to levels associated with past market excesses. This development comes amid already elevated valuations tied to artificial intelligence advancements.

Bank of America Raises Concerns

Michael Hartnett, chief investment strategist at Bank of America, has drawn attention to risks in the current market setup. He points to the potential for technology stocks to exceed 48 percent of the S&P 500’s total market capitalization once certain high-profile companies enter the public markets.

Such a shift would place the index in territory linked to significant historical downturns. Hartnett’s analysis frames this as part of a broader pattern where optimism around a few leading firms drives narrow market leadership.

Upcoming Public Listings in Focus

SpaceX, OpenAI, and Anthropic represent some of the most anticipated initial public offerings on the horizon. These companies operate at the intersection of space technology, artificial intelligence development, and advanced computing infrastructure.

Their combined valuations, potentially reaching trillions of dollars, would add substantial weight to technology holdings in major indexes. Analysts note that these listings could accelerate the trend of market concentration already underway.

Historical Parallels to Earlier Eras

Market concentration at these projected levels would surpass thresholds observed during the Roaring Twenties and other periods of speculative fervor. In those times, a handful of sectors dominated equity benchmarks before corrections took hold.

Similar dynamics appeared in the Nifty Fifty era of the 1970s, Japan’s asset bubble in the 1980s, and the technology surge of the late 1990s. Each case saw elevated weights for leading companies followed by periods of underperformance for the broader market.

Current State of Tech Dominance

Technology stocks already command a significant portion of the S&P 500, with recent figures placing the sector around 39 percent or higher in recent trading. This reflects strong performance among major firms involved in semiconductors, software, and related fields.

The addition of new entrants from private markets would further tilt the balance. Observers point to this narrowing leadership as a source of vulnerability should sentiment toward artificial intelligence investments shift.

Potential Outcomes for Market Participants

Investors face a landscape where gains remain tied to a small group of companies. Strategies that emphasize diversification or exposure beyond dominant technology names may gain consideration as these listings approach.

Hartnett and others have referenced post-bubble playbooks from prior cycles, which often favored sectors outside the previous leaders. The coming months will test whether the current momentum sustains or encounters resistance.