Reliable, internally consistent macro-data is a precondition for sound economic policy. Examine this in light of India's recent revision of GDP, CPI and IIP series.

Interest rates, fiscal targets and industrial incentives are all set using data on GDP, CPI and IIP. In 2026, MoSPI revised the base years of all three: GDP and IIP moved to 2022-23 and CPI to 2024 [3]. These revisions make India's data much more reliable, but some gaps in method remain.

Why reliable, consistent data matters

• Monetary policy: RBI's inflation-targeting framework is based on CPI. An outdated consumption basket gives a wrong inflation rate, and so a wrong policy rate.
• Fiscal policy: deficit and debt targets are measured as a share of GDP. If GDP is measured wrongly, the room for government spending is misjudged.
• Industrial policy: IIP shows which sectors need support. An outdated basket leaves out fast-growing new industries.
• Consistency: if indicators use different base years, output and prices cannot be compared reliably.

How the revision improves reliability

• Matched base years: 2022-23 was chosen for IIP because it was a stable year and it matches the GDP and WPI base [1][2].
• Updated basket: IIP now has 463 item groups, including 120 new ones such as stents, vaccines and CCTV cameras. Old items such as kerosene and CFLs have been dropped [1][2].
• Wider coverage and updated weights: the index now includes minor and rare-earth minerals, gas, and a new water supply, sewerage and waste management sector. Electricity's weight rises to 10.865% and mining's falls to 11.053% [1][2].
• Expert oversight: each revision is guided by a Technical Advisory Committee with members from academia, the states and the RBI [3].

Gaps that remain

• Weights go out of date: IIP uses fixed Laspeyres weights, so the 2011-12 basket stayed in use until 2026. TAC-IIP recommended chain-linking, but so far only as an internal pilot [2].
• Short series: there is no seasonally adjusted IIP yet. Old and new data are linked only at the sector level [2].
• Estimates in place of measurement: value-based items are adjusted for prices using WPI. Water is measured by tap connections, and sewerage data comes only from 500 AMRUT cities [2].

Way forward

• Release the chain-linked and seasonally adjusted series on a fixed timeline.
• Publish linked back-data for sub-sectors, and switch to an Output Producer Price Index for price adjustment.
• MoHUA and MoSPI should extend water-sector data beyond AMRUT cities.

Together, the 2026 revisions give GDP, CPI and IIP a common, up-to-date base, which evidence-based policy needs. Regular chain-linked updates and open back-data would keep India's statistics credible, in line with SDG 17.18 on timely, high-quality data.