What happened on Nov. 5 and 6
On Thursday, Nov. 5, the S&P 500 fell 4.4% (334.89 points) to 7,353.73, the Dow fell 3.4% (1,833.06 points) and the Nasdaq Composite fell 5.5% to 24,315.00, about 11.9% below last month's record, Spectrum News reported. Yahoo Finance's live coverage put the Nasdaq-100 down 6.3% and the chip index (SOX) down 12%. Nvidia fell 9.3%, Spectrum News reported; Yahoo Finance described a drop of more than 9%.
Friday brought a partial rebound. Reuters, via Investing.com, reported the S&P 500 up 0.32% at 7,376.86, the Nasdaq up 1.1% at 24,579.43 and the Dow down 0.46% at 51,285.73, with the semiconductor index up 4.2% and Nvidia up 2.8%. For the week, Reuters said the Nasdaq lost 3.4%, the S&P 500 2.7% and the Dow 0.9%, with the Nasdaq about 10% below its peak.
How much value is gone
Yahoo Finance said the Nasdaq-100's 6.3% fall erased about $2.3 trillion in market value on Nov. 5. That is a one-day estimate for one index; other outlets count different groups of companies and publish different totals, so compare figures only when the list of companies is the same. Nvidia alone is about 24% below its Oct. 6 record close and has shed nearly $1.4 trillion since then, Yahoo Finance reported, after shedding nearly $450 billion in Thursday's session.
"AI has gone on trial several times in this cycle and come away with an innocent verdict." — Adam Turnquist, LPL Financial, via Reuters
What triggered it
Three explanations recur in the coverage, and they are claims, not settled findings.
The midterms. Spectrum News says Democratic wins raised the possibility that governments could force pauses in data-center construction, and that voters across parties say they are wary of AI and dislike power-bill increases caused by data centers. Slower construction would mean fewer chip purchases and less demand for electricity and related services. This is a fear about policy that has not been enacted.
Borrowing costs. Spectrum reports that construction of further AI data centers may slow because of how expensive it has become to borrow money. Its figures are telling: the 10-year Treasury yield was 4.84% on Nov. 5, down from 4.90% the evening before, but 4.95% on election night and above 5.30% a month earlier. Yields fell on the selloff day; they remain high. On Friday, Reuters said a strong October jobs report lifted the chance of a December Fed rate increase to 78% from 70%, per LSEG. Yahoo Finance reported 165,000 jobs added in October against about 65,000 to 70,000 expected.
Valuations. Critics say AI shares had climbed too far, a bubble argument, and Yahoo Finance listed institutional investors, including hedge funds, selling 2026's top performers to lock in gains among the causes. Spectrum added Iran-war and energy-price uncertainty as a further pressure.
The bull case and the bear case
Bulls argue the spending cycle is intact and prices overshot. Keith Lerner of Truist Advisory Services told Reuters, "We are still giving technology the benefit of the doubt." Yardeni Research called the political backlash against AI infrastructure "speed bumps, not roadblocks, even though Wall Street seems to be pricing in the latter," and called Thursday's selloff a buying opportunity, per Yahoo Finance.
Bears point to fragility. Charlie McElligott of Nomura said of the AI trade, "They're shooting the generals," according to Yahoo Finance, a reference to the largest names leading the fall; he added that the unwinding had been "wildly acute" for more than a month. Reuters also noted the rebound was uneven: the Nasdaq still posted a fourth straight weekly decline, and the S&P 500 had its worst week in more than a year.
Neither camp has settled the factual question underneath: whether AI revenue will grow into the capital being spent. Quarterly results and company capital-spending plans will test that; a two-day price move cannot.
What it means for index and 401(k) investors
This article is not investment advice, and we make no price forecast. On concentration, the clearest evidence in this week's coverage is Spectrum News's point that a 1% move in Nvidia, the heaviest weight in the S&P 500 that day, moves the index more than a 1% move in nearly any other U.S. stock. What the record supports is narrow. First, a fund that tracks the S&P 500 or Nasdaq-100 moved with these stocks, because the weights are built that way; Friday's rebound did not undo the week for any major index. Second, one day's drop says little about long-run returns, and analysts quoted above disagree on direction. Third, the useful question for a saver is not whether the bubble is popping but what is actually inside the funds they own and how a retirement plan's default option is built. Plan documents and fund fact sheets list top holdings; those are the source to check, and a licensed adviser is the person to ask about any change.
