Each of Primecap’s ten analysts also manages small amounts in his or her sector. The firm’s founding managers -- Schow, 83; Millias, 69; and Kolokotrones, 65 -- still work every day, Newhall says.

Mitchell J. Milias, co-founder and chairman of Primecap Management Co., will step down at the end of the year as co-manager of three Vanguard Group Inc. funds with combined assets of more than $42 ...