Fretting Away. The end of the longest U.S. government shutdown in history should have drawn a sigh of relief from investors. But any respite from the reopening was overshadowed by rising concerns over AI stock valuations and receding odds for a December rate cut, leading to stocks’ worst day in a month.

The S&P 500 fell 1.7%. The Dow Jones Industrial Average was down 798 points, or about 1.7%. The index is sliding back toward 47,000 after topping 48k for the first time ever yesterday.

The tech-heavy Nasdaq Composite saw the biggest losses on the day. It closed down 2.3%.

“We’re seeing a classic rotation under way,” writes David Miller, chief investment officer and senior portfolio manager at Catalyst Funds. “Investors are taking some profits in megacap tech after an extended AI driven run and reallocating toward more reasonably valued sectors.”

The knock-on effects of the lengthy government shutdown was also weighing on stocks Thursday. Investors, economists, and policymakers have been operating without crucial government data for more than 40 days. All signs suggest that the eventual data rollout will be messy—about the last thing markets need heading into the end of the year.

“We anticipate ongoing challenges with obtaining a clean read—we think Q4 data will likely add more confusion than clarity,” writes Mike Reid, senior U.S. economist at RBC. “Because of this, our strategy is to focus on the broader trends in play, which include persistent inflation and slower growth in 2026.”

Investors are especially concerned that the lack of data could deter the Federal Reserve from cutting interest rates in December. A quarter-point cut was considered a near-certainty about a month ago; today, traders placed the odds at roughly 52%, according to the CME’s FedWatch tool.

Seema Shah, chief global strategist for Principal Asset Management, outlines the challenge facing the Fed in the coming weeks:

The Hot Stock: LyondellBasell Industries +5.1%
The Biggest Loser: Robinhood Markets -8.6%

Best Sector: Energy +0.3%
Worst Sector: Consumer Discretionary -2.5%

A flood of earnings reports from the best-known quantum computing companies has pushed the sector back into the spotlight. Recent declines in the pure-play stocks suggest investors have doubts about the sector’s near-term prospects.

Shares of quantum companies D-Wave Quantum, Rigetti Computing, and IonQ fell 11.4%, 11%, and 10.5%, respectively, today.

While the long-term investment case remains intact, “the recent volatility across emerging tech and AI sectors has tempered near-term investor enthusiasm,” wrote Benchmark analyst David Williams in a note trimming his price target on Rigetti shares Wednesday.

A quick side note—what exactly is quantum computing? Mackenzie Tatananni, Barron’s’ resident quantum expert, explains:

“Unlike traditional computers, quantum systems operate by the laws of quantum mechanics, which opens up a richer mathematical space for problem-solving,” she wrote today.

Quantum computing can streamline a host of intensive processes, such as scientific and financial modeling, making procedures like drug discovery and machine learning more efficient.

The prospect of rising demand for quantum computers has driven shares higher this year, as have a series of technical milestones that have made implementation seem all the more feasible.

For instance, Rigetti shares rose for six days straight in October when the company announced two purchase orders for its latest-generation Novera quantum processor. Rival IonQ also said early this week that it had achieved a near-perfect score in a key reliability metric, which opens the door to “practical quantum solutions across sectors.”

And tech giant International Business Machines, which conducts quantum research, unveiled its “most advanced quantum processor yet” on Wednesday. The chip, called IBM Quantum Nighthawk, is set to be delivered to customers by the end of the year.

Future developments will likely spark more rallies, Mackenzie writes, even though commercial applications of quantum computing remain years away. Read her full story here.

The producer price index for October was originally scheduled for release tomorrow by the Bureau of Labor Statistics. Like other October data, the PPI has been delayed.

• There’s No Inflation Report Today. But Here’s What the Experts Think.

• Tesla Stock Drops Below $400. Retail Investors Keep Buying.

• Verizon Communications to Slash 15,000 Jobs: Report

• AI Data Centers Need More Power Right Now. These Companies Can Deliver It.

• Healthcare Stocks Are Blowing Past the S&P 500. What Could Be Behind the Rally.

Barron’s Live returns on Monday. Barron’s Live features timely and actionable insights for investors. We give you behind-the-scenes conversations with the newsroom, connecting you with our editors and reporters covering the markets, the economy, and more.

Sign up here