Shares of UnitedHealth Group Inc. UNH, -3.67% dropped 3.7% in afternoon trading Thursday, enough to pace the Dow Jones Industrial Average’s DJIA, -0.35% components in declines. The $18.22 price decline in the health insurance company’s stock was shaving about 120 points off the price of the Dow, which was dropping 144 points, or 0.4%. In comparison, the S&P 500 SPX, +0.10% was up 0.1%. The selloff in UnitedHealth’s stock comes after peer Humana Inc. HUM, -17.53% slashed its estimate of 2022 Medicare Advantage membership growth, amid higher-than-expected terminations during the annual election period. Humana’s stock plunged 19.7%.