Inflation in India: CPI, WPI and GDP Deflator

Why do two official reports give different inflation signals?

Imagine that the price of a school notebook rises, cooking oil becomes cheaper, and a new phone costs more. A household feels the combined effect at the checkout counter, while a manufacturer may focus on the price of steel or fuel used in production. A national accounts statistician asks a different question: how have prices changed across the goods and services produced within the economy? These are not competing answers. They are different measurement windows.

Inflation is a sustained rise in the general price level, not simply an increase in one price. Since no authority can record every transaction, statistical agencies construct price indices from selected items, locations and weights. Understanding the Consumer Price Index (CPI), Wholesale Price Index (WPI) and GDP deflator helps an aspirant read economic news without treating unlike indicators as if they were interchangeable.

Start with the index, then calculate inflation

A price index compares the cost or price of a chosen basket with its reference period. The index is commonly set to 100 in that period. If an index moves from 150 to 156 over a year, the year-on-year inflation rate is (156 ÷ 150 − 1) × 100, or 4 per cent. The index level and the inflation rate are different: an index of 156 does not mean inflation is 156 per cent.

Year-on-year inflation compares a month with the same month a year earlier and reduces the effect of recurring seasonal patterns. Month-on-month change compares adjacent months and can reveal a recent turn sooner, but it may be more volatile. A high or low annual rate can also reflect the comparison base. A base effect changes the measured rate because the earlier comparison month was unusually high or low; it does not by itself explain what is happening to prices now.

Disinflation means prices are still rising, but at a slower rate. Deflation means the general price level is falling. Neither term should be used for a fall in the price of a single commodity. An index is an average: some households, firms or regions may experience a different change because their spending or input basket differs.

CPI: the household cost-of-living window

The CPI tracks changes in retail prices of selected goods and services households acquire for consumption. Its weights represent the relative importance of items in household expenditure. A rise in an item with a larger weight generally affects the index more than the same percentage rise in a lightly weighted item. The CPI therefore connects price movements to consumers’ purchasing power, though it is not a personalised measure of every family’s cost of living.

India’s national CPI is compiled by the National Statistical Office under the Ministry of Statistics and Programme Implementation. It publishes rural, urban and combined measures, along with group and item indices. Food and beverages, clothing and footwear, housing, fuel and light, and other consumption groups help explain which components are pushing the headline measure. The Consumer Food Price Index provides a separate view of food-price changes.

The current CPI series uses 2024 as its index reference period, with 2024 = 100. The weight reference period uses the Household Consumption Expenditure Survey 2023–24. In the new series, the all-India weighted item count rose from 299 to 358, including increases in both goods and services. The revision also adopted the COICOP 2018 classification, added online price collection channels and introduced tablet-based collection. These details matter because a basket and its weights should keep pace with how households actually spend.

The CPI is important beyond household budgets. Section 45ZA of the Reserve Bank of India Act provides that the Central Government, in consultation with the Reserve Bank, determines an inflation target in terms of the CPI once every five years. The Monetary Policy Committee determines the policy rate needed to achieve that target, and its decision binds the Bank. For exam purposes, separate the index compiler from the monetary-policy decision maker: MoSPI compiles CPI; the MPC sets the policy rate under the statutory framework.

WPI: prices at the wholesale or producer-facing stage

The WPI tracks price movements of goods at the wholesale level. It is compiled by the Office of the Economic Adviser in the Department for Promotion of Industry and Internal Trade, Ministry of Commerce and Industry. The current published series has a 2022–23 base. WPI components are organised around primary articles, fuel and power, and manufactured products. Because it measures goods at an earlier point in the distribution chain, it can signal cost pressures that may later affect retail prices, but transmission is not automatic or immediate.

WPI does not measure the price basket paid by households and, in its present form, does not cover services. Thus a rise in WPI can coexist with a smaller CPI rise, or vice versa. A change in wholesale input prices can be absorbed in firms’ margins, offset by productivity, passed on with a lag, or never fully passed on if demand is weak. The official WPI series is useful for examining goods-price and input-cost movement, but it is not a substitute for CPI when the question concerns consumer inflation.

When reading WPI releases, note the base year and whether the figure is provisional. Index values from two different base-year series should not be compared as if their levels were on one continuous scale unless the statistical agency has provided a linked series. The rate of change within a consistent series is usually more meaningful than comparing raw index numbers across series.

GDP deflator: a broad measure derived from national accounts

The GDP deflator is an implicit price index derived from nominal GDP and real GDP: (GDP at current prices ÷ GDP at constant prices) × 100. Unlike CPI and WPI, it is not built by directly pricing one fixed consumer or wholesale basket. It reflects price changes for the final goods and services included in domestic production and can change with the composition of output as well as with prices.

This broader coverage is its strength and also a reason it may diverge from CPI. CPI follows household consumption, including imported consumer goods; the GDP deflator covers domestic production represented in GDP, including investment and government output, while imported goods are not domestic output. Its composition is therefore different. A change in export prices or capital-goods prices can affect the GDP deflator even if household retail prices move differently. It is a useful national-accounts concept, not a direct cost-of-living index.

Compare the three without mixing them up

For a Prelims question, match each index to its compiler, stage and coverage. For a Mains answer, explain why divergence is possible before discussing consequences. For example, food supply shocks can raise CPI sharply because food matters to household consumption; a rise in imported machinery prices may not enter the GDP deflator in the same way as it affects domestic capital costs. The size and direction of the effect depend on the index’s scope and weights.

How to interpret inflation for policy and welfare

Demand-pull inflation arises when aggregate demand grows faster than the economy’s ability to supply goods and services. Cost-push pressure comes from higher production or distribution costs, such as energy or intermediate inputs. In practice, these forces can operate together. A supply shock may raise food prices, reduce real incomes and weaken demand elsewhere. A single monthly number cannot diagnose the cause on its own.

Monetary policy can influence demand and expectations, but it cannot immediately grow a harvest or remove a transport bottleneck. If inflation is driven by a temporary supply disruption, rate changes may have delayed effects and impose costs on output. Governments can address supply constraints through logistics, storage, competition, trade or targeted relief, subject to fiscal and distributional considerations. A strong answer should identify the source, affected groups, persistence and available policy tools rather than recommend a rate change for every price increase.

Inflation also has distributional effects. Low-income households often devote a larger share of their budget to essentials, so food inflation can be especially burdensome. Borrowers and lenders are affected differently when actual inflation differs from what contracts anticipated. When prices rise unpredictably, households and firms may find it harder to plan savings, wages, inventories and investment. Stable and credible measurement supports better policy, but the index alone does not settle the policy choice.

Current connection: why the 2024 CPI base matters

MoSPI introduced the CPI series with base 2024 = 100 in 2026. Its updated expenditure weights draw on HCES 2023–24, and the revised basket includes more weighted goods and services than the previous one. The change is a practical example of statistical base revision: an index should reflect evolving consumption patterns and improve measurement, not merely preserve a historical basket indefinitely. The Office of the Economic Adviser also publishes the WPI series with base 2022–23. Always identify the series before quoting an index level or comparing historical numbers.

As checked on 18 October 2026, MoSPI’s public portal lists CPI data using the 2024 base. Monthly releases can be provisional and may later be revised. In answers that cite a recent rate, state the reference month, release status and series base; this prevents a correct number from being attached to the wrong period or series.

Common exam traps and quick revision

• Index versus rate: an index number is a level; inflation is a rate of change over a stated period.
• Disinflation versus deflation: slower price rises are not the same as falling general prices.
• CPI versus WPI: CPI is retail and consumer-oriented; WPI is wholesale and goods-oriented.
• GDP deflator: it is derived from current-price and constant-price GDP, not a fixed retail basket.
• Base revision: weights and items can change; compare series only with a valid linking method.
• Institutional roles: MoSPI compiles CPI, DPIIT’s Office of Economic Adviser compiles WPI, and the MPC determines the policy rate under the RBI Act.

Practice question: Consider the following statements: (1) CPI measures retail prices of goods and services acquired by households. (2) WPI is the index expressed in Section 45ZA for the statutory inflation target. Which is correct? Answer: Statement 1 only. The statutory target is expressed in terms of CPI; WPI measures wholesale goods prices.

Practice question for Mains: Explain why CPI, WPI and the GDP deflator may show different inflation trends. Discuss the implications for monetary policy and household welfare.

Revision takeaway: Before interpreting any inflation number, ask what is priced, whose basket is represented, which base series is used and what time comparison is being reported. Practise related MCQs and revise quick notes on this topic in the IASLadder app.