UnitedHealth Group (UNH -0.01%) has been a solid dividend growth stock for years. Generally, its yield has been fairly low, due to the stock's rising value. Even as the healthcare insurance giant has grown its dividend, its yield hasn't been particularly high or noteworthy. However, with shares of UnitedHealth in a tailspin of late, that's changed. Entering trading this week, the stock's yield was around 3.5% -- close to three times the S&P 500 average of 1.2%. That's not typical for UnitedHealth. Could thi ...