Shanghai Stock Exchange Index-referred to as Shanghai Composite Index, also known as Shanghai Composite Index. Prepared by Shanghai Stock Exchange according to the prices of all listed stocks. It was officially released on July 5th, 199 1, with the code 1 a0001(the number before a is also1).

Algorithm: Taking the official opening date-199065438+February19 as the base period, taking all 8 kinds of stocks in the market at that time as samples, and taking the stock circulation as the weight. The calculation formula is as follows:

Today's stock price index = today's total market price/base period total market price × 100

The total market value is the sum of the product of the closing price of all the stocks on that day and the circulation (there are actually only 8 stocks in the base period).

In case of future capital increase or increase (decrease) of listed stocks, the total market value of the base period must be revised, and the correction formula is:

Total value of new benchmark market = total value of benchmark market before correction × (total market value before correction+change of total market value)/total market value before correction.

Today's stock price index = today's total market price/new benchmark market price × 100.

From the algorithm of Shanghai Stock Exchange Index, we can know that the index is weighted average, and the weight is the total share capital of listed companies, so the stocks with larger total share capital have a greater impact on the stock index. Because the shares of listed companies in China are divided into tradable shares and non-tradable shares, among which the circulating share capital is not consistent with the total share capital, the Shanghai Composite Index often becomes a tool for large institutions to build momentum, which makes the trend of the Shanghai Composite Index inconsistent with the rise and fall of most stocks. This is the problem of exponential "distortion".

The former is usually called index stock. For example, Sichuan Changhong (600839) is the index stock.

Shenzhen Stock Exchange Composite Index-The full name is Shenzhen Stock Exchange Stock Price Composite Index. It was publicly compiled and released on April 4th, 199 1 with the code 2C0 1. The base period is1991April 3rd, and the base period index is 100. The Shenzhen Composite Index takes all listed stocks as a sample and calculates with the total share capital of the base period as the weight.

Algorithm: Today's real-time index = closing index of last trading day × today's real-time total market value/closing total market value of last trading day.

Today's real-time total market value = the market price of each sample stock × the number of shares issued.

The total market value of the last business day is the total market value adjusted according to the changes in the share capital of the sample stocks on the last business day.

It can be found that the overall trend and fluctuation of Shanghai Composite Index and Shenzhen Composite Index are still very similar. The main reason is that these two markets are actually interrelated. Therefore, all the technical analysis methods and tools used in the Shanghai Composite Index can also be used in the Shenzhen Composite Index, and basically similar results can be obtained.

Answer your two questions:

1. Each stock has a maximum decline and increase limit, generally 10%, and ST stock is 5%. Therefore, the maximum fluctuation range of Shanghai Stock Exchange Index and Shenzhen Stock Exchange Index is within the range of 10% decline and 10% increase every day. However, the first day of listing of new shares is not subject to this restriction. Therefore, if more new shares are issued on a certain day, it will affect the Shanghai Stock Exchange Index and Shenzhen Stock Exchange Index on that day.

2. After the mobile return, the index has not changed after the launch of GEM. It can be seen from the calculation methods of the above two indexes. On the same day, regardless of the number of listed companies, the index has no effect, because every listed company has to modify the index.