UnitedHealth Group serves more than 75 million people through its extensive repertoire of assorted health care offerings. Last year it added a few million more clients to its mix, a surprising feat given the sad state of the nation’s unemployment rate.Overall, four of the company’s six main operating units registered sales gains of more than 10%. Notable star: Igenix, UnitedHealth’s data management and information technology unit, whose revenues increased more than 25%. All the more reason UnitedHealth stock is up 53% over the past year. —P.N.