Market data is usually defined as prices for investments which trade on an exchange, such as stock prices from the New York Stock Exchange (NYSE) or futures prices from the Chicago Board of Trade. However, there are trillions of dollars worth of instruments that trade over the counter (OTC), which means they are traded between parties via perhaps simply a phone call backed up by a written agreement.
Besides prices, market data can consist of yields, but also such information as high and low, volume, market capitalization, dividends, earnings forecasts, credit rating, and more. All of these are potentially useful to investors.
Some of this data changes continuously throughout the day, some once each day, and some only rarely (perhaps once per quarter, like earnings reports). Some are available as they change, and others are delayed (for example, free stock quotes often come with a 15 minute delay).
There are many sources of market data online, and our hope is that this page will become an exhaustive list of data from sources around the globe in all markets.
New York Stock Exchange
Chicago Board of Trade
Chicago Mercantile Exchange
Market Implied Corporate Default Rates
Market News and Daily Market Commentary
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