Many millions of people — possibly half the population of the United States — have a personal interest in what happens on the stock exchange. Some are directly concerned because they are part owners of companies through stock; others are holders of government and other listed securities; and yet another group are holders of insurance policies and savings bank accounts, since banks and insurance companies invest much of their assets in listed securities.

A stock exchange is a market for the purchase and sale of securities, such as shares, stocks, and bonds. Such markets have existed for centuries. They had their beginnings in the regular meetings, usually in a coffeehouse or restaurant, of a few men who acted as intermediaries between buyers and sellers. They did this for a commission.