The Consumer Price Index (CPI) for a given year is determined by a specific calculation involving a ratio. This ratio compares the current cost of a basket of goods and services to the cost of the same basket in a base period. Specifically, the current period’s expenditure on a fixed set of items is divided by the expenditure on the same set of items during the base period. The resulting value is then typically multiplied by 100 to express it as an index number.
This calculation provides a crucial metric for understanding inflation or deflation within an economy. By tracking changes in consumer prices over time, policymakers, businesses, and individuals can make informed decisions regarding economic strategies, investment, and wage adjustments. Historically, accurate measurement of consumer price changes has been essential for maintaining economic stability and ensuring fair value in financial transactions.