Economically:
? The definition of index, in a broad sense. The relative number formed by the comparison of any two values can be called exponent;
? The narrow index is a special relative number, which is used to measure the comprehensive changes of multiple projects in different occasions.
? Statistical data designed and calculated according to the prices of some sample stocks, electronic spot or bonds are used to measure the price fluctuation of the stock market, electronic spot or bond market. There are related introductions in the electronic viewing room. In the United States, for example, the common stock price indexes are Dow Jones Industrial Average and Standard & Poor's 500 Enterprise Index. The most famous bond price indices are SalomonBrothersBondIndex and Sheeson-Lehman Bond Index. In China, there are circulation-weighted stock index, CITIC index and Xinhua index produced by Shanghai and Shenzhen stock exchanges.