If index levels then fell, LOR would telephone instructions to Chicago to sell more futures; if they rose, it would buy futures. Futures traded in large volumes and could readily be bought and sold with low transaction costs, making "the protection of very large [portfolios] feasible for the first time.... As of the end of 1986, roughly 80 percent of the dollar value of LOR accounts was protected using futures." (Leland and Rubinstein 1988, p. 8) During the mid 1980s, portfolio insurance became big business.

Donald MacKenzie, An Engine, Not a Camera, loc. 803