AI-linked stocks now account for nearly 45% of the S&P 500, up from ~25% in 2022, per Goldman Sachs. Strong earnings and momentum have driven concentration in mega-cap tech, increasing both upside potential and vulnerability to sentiment shifts.Summary:AI-linked stocks now account for ~45% of S&P 500, per Goldman SachsWeighting has surged from ~25% since late 2022Gains driven by semiconductors, platforms, and AI infrastructure namesStrong earnings and margin expansion underpin re-ratingRising concentration increases sensitivity to sentiment shiftsArtificial intelligence-linked companies are now approaching nearly half of the S&P 500 by market weight, underscoring the extent to which the US equity market has become concentrated around a single dominant theme.Analysis from Goldman Sachs shows that AI-related stocks account for close to 45% of the benchmark index, a sharp increase from roughly 25% at the time of ChatGPT’s launch in late 2022. The shift reflects a powerful re-rating of companies tied to artificial intelligence, including semiconductor manufacturers, cloud infrastructure providers, and large platform firms.The increase has been steady rather than episodic. Index weightings linked to AI have climbed consistently through 2024 and 2025, with only brief pauses, suggesting the move is being driven by both structural demand and sustained investor momentum. Strong earnings growth, improving margins, and rising expectations around AI-driven productivity gains have reinforced the trend.Capital flows have increasingly concentrated in a relatively small group of mega-cap names seen as the primary beneficiaries of the AI boom. These firms have delivered outsized returns and have become the key drivers of overall index performance, effectively masking more mixed performance across the broader market.This type of concentration is not unusual during major technological shifts, but the scale is notable. With close to half of the index tied to AI-related companies, the broader market’s direction is becoming increasingly dependent on the outlook for a single sector and a handful of dominant firms.That dynamic presents a two-sided outcome for investors. On one hand, the concentration reflects strong fundamentals and leadership from companies at the forefront of innovation. On the other, it introduces vulnerability. Any shift in sentiment toward AI—whether driven by valuation concerns, earnings disappointments, or changes in the macro environment—could have an outsized impact on index-level performance.In effect, the S&P 500 is evolving into a more top-heavy, theme-driven index, where the trajectory of AI adoption and monetisation plays a central role in determining market direction. This article was written by Eamonn Sheridan at investinglive.com.