A steep slide in UnitedHealth Group shares was dragging on the Dow Jones Industrial Average on Thursday, putting the blue-chip index on track for historical underperformance versus the S&P 500.

UnitedHealth Group stock crashed on Thursday, falling more than 22% and putting the stock on track for its largest single-day decline since 1998. The slide is a problem for the health insurance giant,

Shares of UnitedHealth took a historic tumble Thursday after the U.S.’ largest health insurer fell far short of Wall Street’s estimates in its quarterly earnings report, dragging down the blue chip Dow Jones Industrial Average with it.