The New York Stock Exchange (NYSE) is a physical exchange, with a hybrid market for placing orders electronically from any location as well as on the trading floor. Orders executed on the trading floor enter by way of exchange members and flow down to a floor broker, who submits the order electronically to the floor trading post for the Designated Market Maker ("DMM") for that stock to trade the order. The DMM's job is to maintain a two-sided market, making orders to buy and sell the security when there are no other buyers or sellers. If a spread exists, no trade immediately takes place – in this case the DMM may use their own resources (money or stock) to close the difference. Once a trade has been made, the details are reported on the "tape" and sent back to the brokerage firm, which then notifies the investor who placed the order. Computers play an important role, especially for program trading.
“ The stock market — the daytime adventure serial of the well-to-do — would not be the stock market if it did not have its ups and downs. (...) And it has many other distinctive characteristics. Apart from the economic advantages and disadvantages of stock exchanges — the advantage that they provide a free flow of capital to finance industrial expansion, for instance, and the disadvantage that they provide an all too convenient way for the unlucky, the imprudent, and the gullible to lose their money — their development has created a whole pattern of social behavior, complete with customs, language, and predictable responses to given events. What is truly extraordinary is the speed with which this pattern emerged full blown following the establishment, in 1611, of the world's first important stock exchange — a roofless courtyard in Amsterdam — and the degree to which it persists (with variations, it is true) on the New York Stock Exchange in the nineteen-sixties. Present-day stock trading in the United States — a bewilderingly vast enterprise, involving millions of miles of private telegraph wires, computers that can read and copy the Manhattan Telephone Directory in three minutes, and over twenty million stockholder participants — would seem to be a far cry from a handful of seventeenth-century Dutchmen haggling in the rain. But the field marks are much the same. The first stock exchange was, inadvertently, a laboratory in which new human reactions were revealed. By the same token, the New York Stock Exchange is also a sociological test tube, forever contributing to the human species' self-understanding. The behaviour of the pioneering Dutch stock traders is ably documented in a book entitled “Confusion of Confusions,” written by a plunger on the Amsterdam market named Joseph de la Vega; originally published in 1688, (...) ”
Stock market participation refers to the number of agents who buy and sell equity backed securities either directly or indirectly in a financial exchange. Participants are generally subdivided into three distinct sectors; households, institutions, and foreign traders. Direct participation occurs when any of the above entities buys or sells securities on its own behalf on an exchange. Indirect participation occurs when an institutional investor exchanges a stock on behalf of an individual or household. Indirect investment occurs in the form of pooled investment accounts, retirement accounts, and other managed financial accounts.
According to one interpretation of the efficient-market hypothesis (EMH), only changes in fundamental factors, such as the outlook for margins, profits or dividends, ought to affect share prices beyond the short term, where random 'noise' in the system may prevail. The 'hard' efficient-market hypothesis does not explain the cause of events such as the crash in 1987, when the Dow Jones Industrial Average plummeted 22.6 percent—the largest-ever one-day fall in the United States.