The S&P 500 has surged 117% since October 12, 2022, riding a wave of artificial intelligence investment that has transformed corporate profits and concentrated extraordinary wealth among a shrinking number of mega-cap technology firms. Three days before the rally’s fourth anniversary, the index traded near record highs. Yet those gains mask a troubling shift in how America’s stock market works.
That concentration matters. The 10 largest companies now account for roughly 40% of the S&P 500’s total value, up sharply from about 28% in October 2022, according to J.P. Morgan Asset Management. Of the 13 U.S. companies with market values exceeding $1 trillion, all but two operate in technology or have significant AI exposure. Nvidia alone has exploded from a $286 billion market value to $5.8 trillion, making it the world’s most valuable company and a stark example of how concentrated this rally has become.
Who’s Actually Benefiting
The gains aren’t spread evenly across the market. Only technology and communication services have outperformed among the 11 S&P 500 sectors during this bull run. Consumer staples and real estate, sectors that employ millions of working Americans, rank among the weakest performers. Energy earnings are up 115% year over year, but that’s largely driven by a 30% surge in oil prices tied to the U.S.-Israeli war with Iran, not sustainable business growth. These gaps show how AI investment rewards a narrow slice of the economy while leaving whole sectors—and their workers—behind.
S&P 500 earnings are expected to rise more than 35% this year overall, yet two-thirds of that increase comes from the technology sector and AI-heavy companies like Alphabet, Amazon.com, and Meta Platforms. Oxford Economics estimates roughly one-third of recent U.S. economic growth stems from AI infrastructure investment and stock-market gains that boost consumer spending among the wealthy. That’s a precarious foundation for broadly shared prosperity.
The Pressure to Deliver
But the easy gains may be behind us. Anthony Saglimbene, chief market strategist at Ameriprise, said: “The AI theme is the defining feature of this bull market. What you're seeing in terms of the bull market four years in is, I think, the easy money around AI has been made.”
Angelo Kourkafas, senior global investment strategist at Edward Jones, pointed directly to the concentration risk: “The risk of concentration is that if the prevailing theme goes out of favor, portfolios might feel it in an outsized way.” His firm is now taking “some of the risk off the table” as fixed income becomes more attractive, signaling cautious skepticism about whether current valuations can hold.
That skepticism matters. Companies must prove that massive AI spending today will translate into profits tomorrow. Nick Raich, CEO of the Earnings Scout, put it this way: “We're still going 100 miles an hour in the AI infrastructure buildout, but three months ago we were going 150 miles an hour.” Earnings estimate revision momentum is cooling. Technology stocks and semiconductor companies reported 136% earnings growth in the third quarter, down from 158% in the second quarter. They’re losing velocity.
Structural Risks Mounting
The Federal Reserve’s pivot toward interest-rate hikes to combat inflation creates additional headwinds. The 10-year Treasury yield has reached its highest level in 24 years, around 5.2%, creating stiff competition for stocks from bonds. Higher borrowing costs disproportionately squeeze sectors that depend on debt financing. Utilities and other heavy borrowers face particular pressure.
Markets also face volatility ahead of next month’s U.S. midterm elections. Any weakness in AI could draw sharp punishment, given how concentrated the rally has become. The bear market before October 2022 coincided with aggressive Fed rate hikes, a scenario that could repeat if inflation remains sticky.
Ryan Detrick, chief market strategist at Carson Group, says this bull run ranks as the eighth-longest since World War Two and the sixth-best-performing. Yet length alone doesn’t signal durability. As Mark Hackett, chief market strategist for Nationwide, observed: “Bull markets don't end of old age; they end from disease.” The question now is whether concentration risk, cooling momentum, rising rates, and narrowing breadth are early symptoms of that disease.
Why This Matters:
This market rally reveals a troubling truth about how wealth concentrates in 21st-century America. When two-thirds of earnings growth comes from a handful of mega-cap AI firms, most workers and investors feel left behind. Consumer staples, real estate, and other sectors employing millions are stagnating. Meanwhile, the Federal Reserve’s rate-hike cycle threatens to slow the broader economy while protecting the wealthy who benefit most from equity gains. The concentration of market power among 13 mega-cap firms creates systemic fragility: if the AI trade falters, average Americans with diversified retirement accounts will absorb outsized losses. Broader economic growth that strengthens labor markets and raises wages for working people, not just stock prices for the already wealthy, remains elusive. Democratic oversight of how AI investment shapes inequality, labor markets, and financial stability has barely begun.