There are clearly cases probably many cases in which finance theory was invoked but in which the invocation had little or no effect on market processes. In the 1970s, for example, many U.S. investment managers learned to talk plausibly about "betas" and paid for beta books, but, as noted above, a good number of them may have understood "beta" in a different way from how finance theorists understood it. Many such managers also seem to have continued in their investment practice much as they always had done, trying to pick "winners," to "buy low," and to "sell high."

Donald MacKenzie, An Engine, Not a Camera, loc. 1136