• The Dow Jones Industrial Average notched its longest daily losing streak in 50 years when it fell for a tenth straight session on Wednesday.
• Wednesday’s drop came after the Federal Reserve scaled back its forecast for interest rate cuts amid uncertainty about the path of inflation in the coming year.
• The declines of the previous nine days came after the killing of a UnitedHealth Group executive put a spotlight on the business of health care, weighing on stocks in the sector and, subsequently, the price-weighted Dow.
• Nvidia, one of the Dow’s newest members, has also trailed the market and dragged down the index in recent weeks.

The Dow Jones Industrial Average tumbled Wednesday after falling in each of the previous nine sessions, capping off its longest stretch of daily losses since 1974.

The blue-chip index has slumped 6% during its latest losing streak. The S&P 500 and the Nasdaq Composite have shed a comparatively modest 3.5% and 1.8%, respectively, despite suffering more painful routs on Wednesday. 

So why have these three major indexes, each containing the stocks of some of America’s largest companies, diverged lately? 

UnitedHealth Group (UNH) shares lost more than 20% of their value in the nine sessions after Dec. 4, the day the CEO of its insurance arm was fatally shot in an attack that’s put renewed focus on the business of healthcare in America. That was also the last day the Dow closed higher.

Since the shooting, lawmakers have introduced legislation to force the breakup of certain big healthcare companies and President-elect Donald Trump has vowed to “take out the middleman,” referring to pharmacy benefit managers (PBMs), who negotiate drug prices on behalf of insurers, employers, and government health plans. 

Shares of CVS Health (CVS) and Cigna (CI), both of which, like UnitedHealth, operate insurance companies and PBMs, fell 24% and 20%, respectively, between Dec. 4 and Tuesday’s close. 

Before its slump, UnitedHealth had a stock price of $610, making it the priciest stock in the Dow, and thus the index’s most influential component. That’s because the Dow is price-weighted, meaning the higher a company’s share price, the bigger its impact on the index. The S&P 500 and Nasdaq, meanwhile, are capitalization-weighted and give more influence to companies with greater market values. 

UnitedHealth hasn’t been the only laggard in the Dow this month. Nvidia (NVDA), which joined the blue-chip index in early November, has fallen in all but one trading session since Dec. 4. The stock, possibly weighed on by reports of an anti-monopoly investigation in China and the ascent of competitor Broadcom (AVGO), entered a technical correction earlier this week. 

The Dow was on track to snap its losing streak on Wednesday before the Federal Reserve’s interest rate projections sparked a broad sell-off. Nvidia shares fell 1.1% on Wednesday after trading more than 3% higher in mid-day trading. UnitedHealth Group was the only component of the 30-stock Dow to close in the green, rising 2.9% alongside peers CVS and Cigna.

Update—December 18, 2024: This article was updated to reflect stock prices and index levels as of the market close on Wednesday.