Even for managers who were doing no more than paying lip service to finance theory, the theory's incorporation into market infrastructure mattered. As chapter 3 suggested, stock-picking managers knew that their investment performance was increasingly being monitored by software-implemented measurement systems. They might not fully have understood those systems' foundations in the Capital Asset Pricing Model, but their behavior changed nonetheless. Many became "closet" index trackers, their self-perceived stockpicking skills limited to modest over-weighting or under-weighting of particular stocks or sectors.

Donald MacKenzie, An Engine, Not a Camera, loc. 1137