S&P 500 loses about $2.9T in market value, the largest one-day loss ever

An AI selloff erased an estimated $2.9T from the S&P 500 on Thursday, MarketWatch estimates, the most market value the index has ever lost in a single day. The S&P 500 (SPY) closed down 4.4%, its worst day since April 2025.

The Dow fell 3.4%.

Tech took the largest share of the losses. The Nasdaq 100 (QQQ) fell 6.4% and lost $2.3T of its value, Bloomberg reports, and the seven biggest tech stocks, the Magnificent 7, lost $1T between them, CNBC said.

Chip stocks fell the most. The PHLX Semiconductor Index dropped 12.3%, and the iShares Semiconductor ETF (SOXX) had its worst day since March 2020, as reported by CNBC. Nvidia (NVDA) fell 9.3%.

The selloff followed Tuesday's midterm elections, as investors grew concerned that Democratic victories could lead to tighter restrictions on data center development and slow AI infrastructure spending.

In Texas, for example, Democrat Gina Hinojosa was elected governor after calling for an immediate moratorium on data center development.

"Any slowdown would raise concerns because the AI growth story has largely depended on the rapid buildout of supporting infrastructure," Melissa Brown of SimCorp told Reuters.

The drop undid Wednesday's rally, when the S&P 500 had its biggest one-day gain in three months.

Sources & Further Reading

1. "Tech stocks log worst day since 2020 as carnage comes to the AI trade." MarketWatch. November 5, 2026.
2. "Wall Street sheds $3.2tn as Democratic midterm sweep triggers brutal AI rout." Financial Times. November 5, 2026.
3. "Tech Stocks Sink on Investors' AI Anxiety." Bloomberg. November 5, 2026.
4. "Magnificent 7 loses $1 trillion. The most eye-popping stats from Thursday's tech stock plunge." CNBC. November 5, 2026.
5. "Nasdaq posts biggest daily drop in 19 months on fears of AI regulations." Reuters. November 5, 2026.
6. "Nasdaq drops into correction territory — here's what typically happens next." CNBC. November 5, 2026.