First, the gross domestic product is measured by the final products and services, that is, the final sales value of the final products and services in this period. Generally speaking, products can be divided into intermediate products and final products according to their practical uses.

The so-called final product refers to the goods and services that people can directly consume or use in a certain period of time. These products have reached the final stage of production, and can no longer be used as raw materials or semi-finished products for producing other products and services such as consumer goods and capital goods, and are generally sold in the final consumer goods market.

Intermediate products refer to goods and services used to produce other products for reprocessing or resale, such as raw materials and fuels. GDP must be calculated according to the final product of the current period, and intermediate products cannot be included, otherwise it will cause double calculation.

Second, GDP is a concept of market value. The market value of various final products is the value exchanged in the market, which is measured by money and reflected by market exchange. The market value of a product is obtained by multiplying the unit price of the final product by its output.

Third, GDP generally only refers to the value caused by market activities. Unproductive activities, underground transactions and black market transactions are not included in GDP, such as housework, self-sufficient production, gambling and illegal drug trafficking.

Fourth, GDP is the final product value produced during the calculation period, so it is flow rather than stock.

Fifth, GDP is not the real wealth in circulation, it just uses the standard monetary average to express wealth. However, it is uncertain whether the products produced can be completely transformed into circulating wealth.