The document discusses the Consumer Price Index (CPI) in Australia. It defines the CPI as an index that measures price changes of a fixed basket of goods and services acquired by household consumers in the eight capital cities. It describes how the CPI is used by government agencies, analysts, and lobby groups to track inflation. The document also outlines some limitations of the CPI, how it is compiled through quarterly price quotations of over 100,000 items, and how it is calculated using a Laspeyres formula. It discusses special cases like spatial price indexes that compare prices across different capital cities.