A measure of how much price-earnings ratios among the 50 biggest companies vary has fallen to almost the lowest on record, data compiled by Bloomberg show. Such rotations, which can be done with a click of a button using exchange-traded funds, show buyers are making too few distinctions among good and bad companies and could exacerbate selling once it begins, said Eric Schoenstein, co-manager of the $5.2 billion Jensen Quality Growth Fund.