WPI vs CPI vs GDP Deflator: The Price Index Memory Map That Ends India's Inflation Mix-Up

Diagram: a side-by-side comparison of WPI, CPI-Combined, CPI-IW/CPI-AL and the GDP Deflator, showing what each measures, who releases it, its base year, and the one index the RBI targets.

1. Wholesale Price Index (WPI)

Released by - The Office of the Economic Adviser, Department for Promotion of Industry and Internal Trade (DPIIT), Ministry of Commerce & Industry - not the statistics ministry.
Mnemonic Hook: "WPI sits with the Commerce Ministry, not with MoSPI."

What it measures - Prices at the first point of bulk/wholesale sale, i.e. the producer or trader level, before goods reach a retail shelf. It excludes services completely.
Mnemonic Hook: "WPI never meets a customer" - no services, no retail margin, no shop counter.

Basket - Fixed-weight (Laspeyres-type) index built from three groups: Primary Articles, Fuel & Power, and Manufactured Products.
Link: Manufactured Products carries the heaviest weight in the WPI basket, which is why factory-gate price shocks move WPI faster than CPI.

Base year - Old base 2011-12; a new base year of 2022-23 has been approved, with the commodity basket widened from 697 to 957 items and weights now derived from Gross Value of Output.
Mnemonic Hook: "2011-12 bows out, 2022-23 moves in."

2. Consumer Price Index (CPI) - the National Series

Released by - The National Statistical Office (NSO), Ministry of Statistics & Programme Implementation (MoSPI).
Mnemonic Hook: "CPI = Consumer + Central statistics office (MoSPI), the mirror image of WPI's Commerce Ministry."

What it measures - Retail prices actually paid by households, published as CPI-Rural, CPI-Urban and CPI-Combined. It includes services (education, health, transport, recreation) that WPI leaves out.
Link: CPI-Combined is the number quoted in every monthly "retail inflation" headline.

Why it matters most - Under the flexible inflation-targeting framework, the RBI is legally bound to keep CPI-Combined inflation at 4% (+/- 2%) - not WPI inflation.
Mnemonic Hook: "CPI drives the Repo Rate; WPI does not."

Base year - Old base 2012=100; a new 2024=100 series begins publishing from January 2026 (old series data stops December 2025), built on fresh weights from the Household Consumption Expenditure Survey (HCES) 2023-24, and for the first time it captures rural house rent. The two series are not directly comparable.
Mnemonic Hook: "2012 to 2024 - a 12-year jump, and rural rent finally joins the basket."

3. The Other CPIs - Labour Bureau Series

CPI for Industrial Workers (CPI-IW) - Compiled by the Labour Bureau, Ministry of Labour & Employment (not MoSPI). Base year 2016=100 (revised from 2001). Used to calculate and revise Dearness Allowance (DA) for central government employees and wage indexation for industrial workers.
Mnemonic Hook: "IW = Income for Workers' DA."

CPI for Agricultural Labourers (CPI-AL) - Also compiled by the Labour Bureau. Still runs on the old base year 1986-87=100 - it has never been revised. Used to revise minimum wages for agricultural labour.
Mnemonic Hook: "AL = Agricultural Labour, an Ancient base-year still Alive (1986-87)."

Link: Both CPI-IW and CPI-AL sit administratively with the Ministry of Labour & Employment, while CPI-Combined sits with MoSPI - a favourite UPSC trap that tests whether aspirants know there isn't one single "CPI office."

4. GDP Deflator

Formula - GDP Deflator = (Nominal GDP / Real GDP) x 100. Released quarterly and annually by the NSO alongside the GDP estimates themselves, on the 2011-12 base.
Mnemonic Hook: "No shopping basket, no field survey - the deflator is simply GDP's own shadow price."

Coverage - The widest of all three: every final good and service produced domestically, including investment goods, government services and exports. Imported goods are excluded (unlike CPI, which does include the retail price impact of imported goods on domestic shelves).
Link: Because it covers all domestic output, the GDP Deflator can sit between WPI and CPI, or even outside their range, in any given quarter.

Weights - Not fixed. The deflator re-weights itself automatically every year to match that year's actual output mix, unlike the fixed Laspeyres baskets of WPI and CPI.
Mnemonic Hook: "Deflator = Domestic coverage, Dynamic weights, never the Dial RBI watches."

5. The 2025-26 Base-Year Overhaul - Why Two Indices Changed Almost Together

What changed - WPI's new base (2022-23) and CPI's new base (2024=100) were approved and rolled out within the same broad window, alongside the Index of Industrial Production (IIP). WPI's basket widened to 957 items with renewable energy sources added under electricity and crude petroleum/natural gas reclassified into Fuel & Power; CPI's new weights came from HCES 2023-24.
Mnemonic Hook: "Same season, two reboots - WPI got wider (957 items), CPI got closer to real rent."

Where WPI is headed - The existing WPI series will run in parallel for five years before being discontinued, as it is gradually replaced by a formal Producer Price Index (PPI) framework: an Output PPI, an Input PPI, and a Services PPI covering seven sectors (banking, securities, insurance, pension funds, railways, air transport and telecommunications).
Link: This shift aligns India's price statistics architecture with IMF recommendations and the practice already followed by most advanced economies.

Quick Timeline/Flowchart

1986-87 - CPI-AL base year fixed (still unchanged today)
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2001 - CPI-IW base year set (pre-revision)
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2011-12 - WPI and GDP (National Accounts) base year set
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2012 - CPI-Combined base year set (=100)
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2016 - CPI-IW base year revised
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2022-23 - New WPI base approved; PPI framework (OPPI, IPPI, Services PPI) cleared
↓
2023-24 - HCES conducted, feeding new CPI weights
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January 2026 - CPI 2024=100 series begins publishing; CPI 2012 series retired

Quick Revision List

• WPI: wholesale/producer prices, excludes services, released by the Economic Adviser (DPIIT, Commerce Ministry); base shifting from 2011-12 to 2022-23.

• CPI-Combined: retail prices, includes services, released by the NSO (MoSPI); base shifting from 2012 to 2024=100 from January 2026; this is the index the RBI targets at 4% (+/-2%).

• CPI-IW and CPI-AL: compiled by the Labour Bureau (Ministry of Labour), used for DA revision and agricultural minimum wages; bases are 2016 and 1986-87 respectively.

• GDP Deflator = Nominal GDP / Real GDP x 100; broadest coverage, self-adjusting weights, base 2011-12; never used as an RBI inflation target.

• Only CPI-Combined inflation feeds directly into monetary policy decisions - not WPI, not the deflator.

• WPI is being phased out over five years in favour of a dedicated Producer Price Index (PPI) framework.

Common Confusion Traps

• "WPI inflation is what the RBI controls": False - the RBI's statutory mandate targets CPI-Combined inflation, not WPI.

• "CPI and WPI must always move together": False - WPI (no services, wholesale-level) and CPI (includes services, retail-level) can diverge sharply, for example when wholesale commodity prices fall even as retail services inflation stays sticky.

• "There is only one CPI with one base year": False - CPI-Combined (2024=100 from Jan 2026, MoSPI), CPI-IW (2016=100, Labour Bureau) and CPI-AL (1986-87=100, Labour Bureau) are three separate series with three different custodians.

• "The GDP Deflator is built from a fixed basket survey like CPI/WPI": False - it has no survey basket at all; it is derived arithmetically from national accounts data (Nominal GDP / Real GDP), so its implicit weights shift every year.

• "The new CPI 2024 series can be directly compared with the old CPI 2012 series to compute long-run inflation": False - differing item baskets, weights and market coverage make the two series non-comparable without a linking factor.