Nasdaq Faces Potential 30% Crash If AI Bets Disappoint, Siegel Says

Jeremy Siegel of WisdomTree has warned that the Nasdaq Composite could decline by as much as 30%. The risk increases if AI capital expenditure does not produce the anticipated returns.

This caution arrives on the 39th anniversary of Black Monday, when markets are assessing if AI can regain its momentum.

BREAKING: The Nasdaq 100 closes the day up +1.1%, posting its best day since September 21st.

The S&P 500 added +$300 billion in maket cap today. pic.twitter.com/LgPtW9ItRD

— The Kobeissi Letter (@KobeissiLetter) October 19, 2026

How AI Expenditure Is Elevating Nasdaq Vulnerability

Concentration risk refers to the vulnerability an index faces when a handful of large corporations or investment themes account for most of its value. Because the Nasdaq is significantly tilted toward AI-related tech shares, a change in that trend can sway the entire benchmark.

Siegel has often pointed out dangers in AI capital outlays. He has likened the present cycle to past episodes. In those cases, genuine demand existed, yet surplus capacity eventually squeezed profits for the largest investors. That track record makes the current discussion more difficult to overlook.

Multiple factors drove last week's market swings. Worries about AI funding and debt offerings from hyperscal companies dampened investor mood.

Rising oil costs, increased bond yields and a jump in the VIX also contributed to the strain. The Nasdaq Composite ended Friday's session at 26,140, following a 2.15% decline. It recorded its weakest weekly performance since June, losing approximately 4.5%.

On Monday, the Nasdaq rallied up to 1.8%, reaching a high near 26,600 around the middle of the day, driven by semiconductor and AI-infrastructure names.

The index pulled back during the afternoon session but remained positive, closing up 1 .11% at 26,430.89. The S&P 500 also gained ground, while the Dow Jones Industrial Average was largely unchanged.

Meta Platforms and Tesla are about to release their earnings, and market participants are observing if AI-related expenditure converts into higher revenue. The recent decline has been seen as a temporary lull by investors, and the recovery persisted until the end of trading.

Can AI Letdown Lead to 30% Nasdaq Fall?

Siegel's analysis suggests a repricing centered on technology-oriented equities.

If AI capital expenditure consistently fails to generate lasting earnings, a significant market correction could be triggered. Under that scenario, the downturn could hit around 30%.

AI-linked stocks account for a record-large portion of total market capitalization, so any letdown could affect growth shares extensively. This concentration contributes to the feasibility of such a scenario. Interest rates are also a factor, as they influence the cost of borrowing for large-scale AI investments.

Siegel remains positive on AI over the long haul, but a steep intermediate correction has emerged as a more distinct near-term threat.

Market participants will scrutinize upcoming earnings reports and capital expenditure data for signs that productivity and revenue boosts are persisting.

Siegel's caution is contingent, yet it underscores the degree to which the benchmark relies on a single investment narrative.