S&P 500 Hits First Record Since August as AI Rally Pushes Market Cap Past $71 Trillion

The S&P 500 climbed 0.6% on October 6, 2026, to strike its first record closing high since August, putting it on course for its 28th record close of the year. The index surpassed the 7,835 level intraday, pushing the combined market cap of its 500 components above $71 trillion for the first time in history. The Nasdaq Composite posted a second consecutive record close, ending at 27,638, up 0.59%, while the Dow Jones Industrial Average gained 187 points, or 0.37%, to 51,455. Analysts noted the US market has added roughly $15 trillion in total market cap since its March 2026 bottom.

The rally was driven overwhelmingly by AI-linked technology and megacap names. Nvidia hit a record high and approached a $6 trillion market cap, with AMD also rallying on reports of stronger AI-driven demand. The S&P 500 software and services index rose 1.3% to its highest level since November 2025, with Salesforce and ServiceNow among the contributors, as fears that AI would disrupt legacy software businesses were increasingly downplayed by investors. Nvidia, Apple, and Microsoft collectively account for roughly 21% of the S&P 500, a concentration that some strategists flagged as a risk even as indices climbed.

Macro conditions were supportive. The 10-year Treasury yield held near 5.28% but moderated slightly from recent multi-decade peaks, and Brent crude slipped below $100 per barrel, easing inflation pressure across equity markets. The CBOE Volatility Index hovered near 15.52, signaling stable risk appetite. Constellation Energy was the top mover in both the S&P 500 and Nasdaq 100, surging roughly 13% on the day, while nuclear stocks more broadly posted strong gains. Marvell Technology rallied after holding its annual investor day, pulling Broadcom higher in sympathy.

Among individual movers, PayPal gained 2.90% and Block rose 2.77% as fintech shares rebounded. On the downside, Merck fell 3.23%, weighing on healthcare, while Cenovus Energy slid 2.93% tracking lower crude prices, and Salesforce dropped 2.14% amid mixed trading in enterprise cloud applications. Johnson and Johnson declined 1.26% as investors rotated out of defensive non-cyclicals.