Take the Capital Asset Pricing Model, for example. It had aspects that were broadly compatible with how practitioners thought about stocks. When the computers and data sets of the 1960s and the 1970s were used to calculate betas, it usually turned out that low-beta stocks were those that practitioners regarded as stable, "defensive" investments, whereas a high beta generally indicated a riskier "growth" stock. So far so good, from a traditional practitioner's viewpoint. The CAPM could, however, also be turned into a disciplinary device, subjecting investment managers' results to mathematical scrutiny.

Donald MacKenzie, An Engine, Not a Camera, loc. 356