Stocks' Biggest Gains Are an Inside Job

``Companies purchasing their own shares represent the single biggest category of stock buyers today, according to a study this month by Jeffrey Kleintop, chief market strategist at brokerage firm LPL Financial... The pullback by traditional investors helps explain why stocks have had trouble making progress at various points this year, money managers say. And the increasing prominence of corporate buybacks has drawn criticism from some in the investment world.''