According to the Census and Statistics Department of the HKSAR, the Consumer Price Index (CPI) measures the changes over time in the price level of consumer goods and services generally purchased by households. The year-on-year rate of change in the CPI is widely used as an indicator of inflation affecting consumers. The Government and some private companies may adjust their service charges or allowances based on this rate of change. Some employers also make reference to this indicator when adjusting salaries and wages.
There are 4 categories of CPI: CPI(A), CPI(B) and CPI(C) respectively relate to households in the relatively low, medium and relatively high expenditure ranges. Meanwhile, a Composite CPI with reference to the overall expenditure patterns of all of the above households are taken together to reflect the impact of consumer price changes on the household sector as a whole.