PPI, like CPI, is one of the important indicators reflecting price changes. PPI belongs to the production side, while CPI belongs to the consumption side. In theory, the long-term trends of the two are consistent. PPI, as a price level indicator in the production process, will transmit its changes to the consumer end through the industrial chain and show a trend similar to CPI. Therefore, PPI is usually regarded as a leading indicator of CPI, that is, PPI generally shows price changes before CPI. Moreover, PPI and CPI are commonly used to assess inflation