The problem, though, was that many portfolio insurance accounts were then "stopped out." They were in effect completely in cash (the futures sales needed to try to protect "floors" had been equivalent to the entire insured portfolio), and the only way in which LOR or the other portfolio insurers could continue to guarantee the "floor" was to leave them in that condition (see, for example, Rubinstein 1988, p. 40). Unless insurers' clients were prepared to accept an ad hoc downward revision of their floors, they thus had entirely to forgo the benefits of subsequent stock-price rises. Given the extent to which stock prices recovered, that turned out to be a significant cost.

Donald MacKenzie, An Engine, Not a Camera, loc. 843