AI Leaders Power Most of 2026 S&P 500 Gains, Jefferies Says

Jefferies says earnings growth, not richer multiples, is driving the move.

Overview

AI stocks make up more than 80% of this year’s S&P 500 advance, with the index up only 2% if those names are excluded.
Jefferies attributes the surge to earnings, noting AI forward estimates are up over 30% since mid‑2025 and the group trades near 25 times earnings with a 0.6 PEG.
AI-linked companies now represent about 45% of the S&P 500’s value, leaving index investors far more exposed to a single theme.
Roughly $1.4 trillion in AI‑related borrowing raises the risk of sharper losses if growth stalls or lending conditions tighten.
Samsung crossed $1 trillion in market value, joining Nvidia, TSMC and Broadcom in the hardware tier, while Q1 results showed 86% of S&P 500 firms beat estimates with outperformance concentrated in AI.