Consumer Price Index

The Consumer Price Index (CPI) is a statistical measure that tracks the weighted-average change in retail prices of a representative basket of consumption goods and services purchased by households over a defined reference period. It is the most widely used indicator of retail (or cost-of-living) inflation, and is constructed using the Laspeyres formula, which holds the base-year basket and weights fixed while measuring price movement. In India, CPI is compiled by the National Statistical Office (NSO) under the Ministry of Statistics and Programme Implementation (MoSPI), with the current series carrying base year 2012 (2012=100). The Labour Bureau separately maintains CPI for Industrial Workers (CPI-IW), used for dearness allowance computation, while the NSO publishes CPI (Combined), CPI-Rural and CPI-Urban. In the United States, the Bureau of Labor Statistics (BLS) within the Department of Labor publishes the CPI-U and CPI-W series, central to the FSOT economics syllabus.

The index works by assigning weights to broad categories — food and beverages, housing, clothing, fuel, transport, health and education — based on consumption-expenditure surveys, and then computing how the cost of that fixed basket changes relative to the base period. The headline CPI inflation rate is the year-on-year percentage change in the index. Variants include core inflation, which strips out volatile food and fuel components to reveal underlying demand pressures, and the GDP deflator, which differs because CPI covers only consumer goods whereas the deflator spans all domestically produced output. CPI differs structurally from the Wholesale Price Index (WPI), which measures prices at the producer/bulk level and excludes services. Following the recommendations of the Urjit Patel Committee (2014), the Reserve Bank of India formally adopted CPI (Combined) as its nominal anchor.

Under the Reserve Bank of India Act amendment of 2016 establishing the flexible inflation-targeting framework, the Monetary Policy Committee (MPC) is mandated to keep CPI inflation at 4 percent, within a tolerance band of plus or minus 2 percent (i.e. 2–6 percent). Failure to keep inflation within this band for three consecutive quarters obliges the RBI to report to the central government. As of 2026 this target, renewed in 2021 for a further five-year term, remains operative, and the MPC calibrates the repo rate primarily against CPI projections. In the United States, the Federal Reserve targets 2 percent inflation but references the Personal Consumption Expenditures (PCE) price index rather than CPI, a distinction frequently tested in comparative questions.

For the UPSC Indian Economy paper (Prelims and General Studies Paper III), CPI is tested on the compiling agency, base year, the WPI–CPI distinction, and its role as the RBI's inflation-targeting anchor — a perennial favourite given recurrent food-price spikes. Aspirants must distinguish CPI-IW, CPI-AL (Agricultural Labourers) and CPI (Combined) and their respective uses, and know that DA revisions track CPI-IW. For the FSOT Job Knowledge test, candidates should grasp BLS methodology, the CPI-U/CPI-W split, the role of CPI in indexing Social Security benefits and tax brackets, and how CPI relates to real-versus-nominal income. The typical question angle probes either the institutional custodian or the policy linkage to monetary targeting.