The concept of statistical index

Exponent (Index) has a broad sense and a narrow sense. Broadly speaking, all relative numbers indicating the overall quantitative changes of social and economic phenomena are indexes. For example, the closing price of a stock on the current trading day is 78.5 yuan, and the closing price of the previous trading day is 73.5 yuan, so it can be calculated that the price index of the stock is 1.068(=78.5/73.5) or 106.8%, indicating that the price of the stock has increased by 6.8%. This index reflects the changes of a single commodity over time. However, in real life, we often have to face the comprehensive changes of many commodity prices. For example, as far as the stocks in this example are concerned, people often hold more than one stock. If we want to reflect the comprehensive changes of all the stock prices held, then the concept of narrow index will be involved.

In a narrow sense, the statistical index (Statistical index) is the relative number indicating the comprehensive change of the total number of complex social and economic phenomena. The so-called complex socio-economic phenomenon population refers to those populations that cannot be directly summed up or compared when studying quantitative characteristics because of the different nature of each part. For example, to reflect the comprehensive changes of three commodities in the market, such as pork, eggs and cauliflower, we can’t add 1 kg of pork, 1 kg of eggs and 1 kg of cauliflower directly, because they are different commodities, and it is meaningless to add them up. Therefore, the population composed of different products or commodities is a complex population. To reflect the comprehensive changes of the complex population quantity, we should not simply adopt the general relative number method, but have a special and special method. Statistical index is a kind of method to reflect the comprehensive change of complex population quantity. Using the principle and method of statistical index, the comprehensive changes of physical quantity and price of different products or commodities can be reflected by compiling physical quantity index and price index.

Both generalized statistical index and narrow statistical index are widely used in practice. However, from the perspective of index theory and method, the statistical index mainly studies the narrow index.