A stock index is a stock price index (an indicator that describes changes in the overall price level of the stock market), and a stock price index is a statistical relative number of stock prices compiled to measure and reflect the overall price level of the stock market and its changing trend. Usually, the average stock price or stock market value in the reporting period is compared with the selected stock average price or stock market value, and the ratio of the two is multiplied by the index value of the base period, which is the stock price index in the reporting period. When the stock price index rises, it indicates that the average price level of the stock rises; when the stock price index falls, it indicates that the average price level of the stock decreases; it is a barometer that reflects the social, political, and economic changes in the country (or region) where the market is located.