With this method, developments in prices can be decomposed into those of "flexible CPI" and "sticky CPI" -- with the former comprising items with relatively high frequency of price changes and vice versa for the latter. Broadly speaking, the flexible CPI is mainly composed of goods prices and the sticky CPI is mainly composed of services prices.
Let me examine variation factors influencing the two aforementioned CPI categories based on the concept of the Phillips curve, which is frequently used in macroeconomic analysis. The flexible CPI is considered to be susceptible to the business cycle or the output gap, whereas the sticky CPI is deemed to be susceptible to medium- to long-term inflation expectations.