U.S. equities closed lower on Monday, July 13, 2026, but the headline indices masked a far more dramatic divergence beneath the surface. The PHLX Semiconductor Index tumbled 4.78%, its steepest slide in months, while the S&P 500 fell a comparatively modest 0.79% to 7,515.34. The S&P 500 Equal Weight Index, which treats every constituent equally, slipped just 0.05%, highlighting how a handful of mega-cap tech names drove the losses.
The gap between the two S&P 500 versions was 0.74 percentage point, underscoring the outsized influence of large-cap stocks. The Nasdaq Composite dropped 1.55% to 25,873.18, while the Dow Jones Industrial Average eased 0.26% to 52,498.64. The moves appeared tied to a revaluation of AI-heavy names rather than a broad selloff, with the chip index losing 6.1 times as much as the S&P 500.
Declining issues outnumbered advancers by a 1.57-to-1 ratio on the New York Stock Exchange and 1.89-to-1 on the Nasdaq. Technology was the worst-performing S&P 500 sector, while energy led all groups. Ross Mayfield, investment strategy analyst at Baird, described moves in memory and chip stocks as “incredibly volatile.”
Memory stocks were in the spotlight. SK Hynix’s American depositary receipts (NASDAQ:SKHY) fell sharply after debuting on Friday. The ADRs priced at $149 and closed their first session at $168, but slid Monday. SK Hynix captured 58% of first-quarter high-bandwidth memory revenue, used in AI applications, while Samsung Electronics (OTC:SSNLF) and Micron Technology (NASDAQ:MU) each held 21%. Phil Blancato of Ladenburg Thalmann said he didn’t see this as “the end of the run,” but Morningstar (NASDAQ:MORN) analyst Jing Jie Yu flagged potential “price erosion” as new supply is expected in 2027 and 2028.
Oil prices surged, providing a hedge but also stoking macro concerns. Brent crude jumped 9.59% to close at $83.30 a barrel, and U.S. West Texas Intermediate rose 9.42% to $78.14. The rally followed reports of a U.S. naval blockade set for Tuesday, reviving fears of disruptions at the Strait of Hormuz. Energy stocks caught a bid, but traders weighed the implications for inflation.
Treasury yields rose on those worries. The 10-year yield gained 2.85 basis points to 4.598%, while the two-year yield hit 4.248%, a level not seen since February 2025. Higher yields can pressure growth stocks that depend on future profits, adding to the headwinds for tech.
Tuesday promises to be a pivotal session. The June consumer price index is due before the open, and JPMorgan Chase (NYSE:JPM) and Goldman Sachs (NYSE:GS) kick off bank earnings. LSEG forecasts 23.7% aggregate profit growth for the S&P 500 in the second quarter. “There were a lot of factors coming to a head all at once,” said Michael Reynolds, strategist at Glenmede.
The setup could reverse quickly. A weaker inflation print or relief at Hormuz may unwind the oil and yield trades and draw buyers back to chips. The risk: if inflation stays firm and Brent remains above $80, what is now a valuation hit for a few names could spill into a wider selloff.
Another pressure point lies in bank earnings calls. Hyperscalers—the top cloud and AI-infrastructure firms—drove a 32% jump in U.S. investment-grade corporate bond supply for 2026 through July 10, according to Bank of America (NYSE:BAC) research. That puts comments about AI-related underwriting and bond holdings in focus, after chip names dragged on the index.
