What do you mean by "Shenzhen Stock Exchange" and "Shanghai Stock Exchange", which are often mentioned in the stock market, rising or falling, hundreds of points and thousands of points? What concept?

The stock index is the stock price index. It is a reference index compiled by stock exchanges or financial services institutions to indicate changes in the stock market. Due to the volatility of stock prices, investors are bound to face market price risks. It is easy for investors to know the price changes of a specific stock, but it is neither easy nor annoying to know the price changes of various stocks one by one. In order to adapt to this situation and need, some financial service institutions make use of their professional knowledge and the advantages of being familiar with the market to compile stock price indexes and publish them publicly as indicators of market price changes. Based on this, investors can test the effect of their investment and predict the trend of the stock market. At the same time, the press, company bosses and even political leaders also use this as a reference index to observe and predict the social, political and economic development situation.

This stock index, that is, the average price indicating the changes in the stock market. A stock index is usually compiled based on a certain month of a year, and the stock price in this base period is 100. The stock prices in subsequent periods are compared with the base period price, and the percentage of rise and fall is calculated, which is the stock index of this period. Investors can judge the trend of stock price according to the rise and fall of the index. And in order to reflect the trend of the stock market to investors in real time, almost all stock markets will announce the stock price index at the same time as the stock price changes.

There are three factors to be considered in calculating the stock index: first, sampling, that is, extracting a few representative constituent stocks from many stocks; The second is weighted, weighted average by unit price or total value, or unweighted average; The third is a calculation program, which calculates arithmetic average, geometric average, or considers price and total value.

Because there are many kinds of listed stocks, it is an arduous and complicated task to calculate the average price or index of all listed stocks, so people often choose a few representative sample stocks from listed stocks and calculate the average price or index of these sample stocks. Used to indicate the general trend and fluctuation range of stock prices in the whole market. When calculating the average or index of stock prices, the following four points are usually considered:

(1) sample stocks must be typical and common. Therefore, when selecting sample stocks, factors such as industry distribution, market influence, stock grade and appropriate quantity should be considered comprehensively.

(2) The calculation method should have high adaptability, and can make corresponding adjustments or corrections to the rapidly changing stock market, so that the stock index or average value has good sensitivity.

(3) There should be scientific calculation basis and means. The calculation basis must be unified, generally based on the closing price, but with the increase of calculation frequency, some are calculated at the hourly price or even shorter time.

(4) The base period should be well balanced and representative.