How securities are traded plays a critical role in price determination and stability

Financial markets are complex organizations with their own economic and institutional structures that play a critical role in determining how prices are established—or “discovered,” as traders say. These structures also shape the orderliness and indeed the stability of the marketplace. As holders of subprime collateralized debt obligations and other distressed debt securities found out in the months following the August 2007 onset of the financial turmoil that led to the global economic crisis, some types of market arrangements can very quickly become disorderly, dysfunctional, or otherwise unstable.

There are two basic ways to organize financial markets—exchange and over the counter (OTC)—although some recent electronic facilities blur the traditional distinctions.

Trading on an exchange
Exchanges, whether stock markets or derivatives exchanges, started as physical places where trading took place. Some of the best known include the New York Stock Exchange (NYSE), which was formed in 1792, and the Chicago Board of Trade (now part of the CME Group), which has been trading futures contracts since 1851. Today there are more than a hundred stock and derivatives exchanges throughout the developed and developing world.

But exchanges are more than physical locations. They set the institutional rules that govern trading and information flows about that trading. They are closely linked to the clearing facilities through which post-trade activities are completed for securities and derivatives traded on the exchange. An exchange centralizes the communication of bid and offer prices to all direct market participants, who can respond by selling or buying at one of the quotes or by replying with a different quote. Depending on the exchange, the medium of communication can be voice, hand signal, a discrete electronic message, or computer-generated electronic commands. When two parties reach agreement, the price at which the transaction is executed is communicated throughout the market. The result is a level playing field that allows any market participant to buy as low or sell as high as anyone else as long as the trader follows exchange rules.

Electronic trading has eliminated the need for exchanges to be physical places. Many traditional trading floors are closing, and orders and executions are now all communicated electronically. The London Stock Exchange and the NASDAQ Stock Market are completely electronic, as is Eurex, a major futures exchange. Many others offer both floor and electronic trading. The NYSE bought the electronic trading platform Archipelago and is moving increasingly toward electronic trading, as is derivatives exchange CME Group, which maintains both open-outcry and electronic trading. Brazil’s BM&F maintained both until 2009.

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