GDP data row: What is the Base Year, how is it revised and why has it raised a political storm? | Explained
The Ministry of Statistics and Programme Implementation (MoSPI) released a new series of GDP estimates with the base year updated from 2011-12 to 2022-23, published on 27 February 2026.
The revision also updates the base years for related indicators: the Index of Industrial Production (IIP) to 2022-23 and the Consumer Price Index (CPI) to 2023-24.
Under the new series, GDP levels for 2022-23, 2023-24, and 2024-25 came in lower than under the old 2011-12-based series, while the reported growth rate for the most recent quarter rose.
A former Finance Secretary publicly questioned the revised figures, arguing that comparing the new base-year GDP for one quarter against the old base-year GDP for the year-ago quarter overstated the reported growth rate.
MoSPI issued a detailed rebuttal stating that cross-series comparison of this kind is methodologically invalid, since a base-year revision changes the entire time series, not just the latest data point, and reiterated that the revision is a routine statistical exercise mandated periodically to keep national accounts current.
What Is a GDP Base Year, and Why Is It Revised?
The base year is the reference year against which real (inflation-adjusted) GDP growth is measured; all other years' output is valued at the base year's prices to strip out the effect of price changes and isolate real volume growth. Periodic base year revisions incorporate updated surveys, newer classification of economic activities, and better-quality source data that were unavailable when the previous base year was fixed.
Key Details
- GDP is compiled by the National Accounts Division of MoSPI (formerly the Central Statistical Organisation, CSO).
- India has revised its national accounts base year multiple times: 1948-49 → 1960-61 (1967) → 1970-71 (1978) → 1980-81 (1988) → 1993-94 → 1999-2000 → 2004-05 → 2011-12 (January 2015) → 2022-23 (February 2026), making the 2022-23 series the latest in a series of roughly decadal revisions.
- The base year is typically chosen to be a "normal" year without major economic shocks, with 2022-23 selected partly because it is a stable post-pandemic year with comprehensive survey data available across sectors.
- Base year revisions typically also update the "basket" of goods and services and their relative weights, reflecting structural changes in the economy since the previous base year (e.g., growing weight of services, digital economy activity).
The 2011-12 to 2022-23 shift is the latest in this decadal cycle, driven by the availability of newer survey rounds and the need to reflect a more current economic structure, exactly as prior revisions (e.g., 2004-05 to 2011-12) were justified.
Advisory Committee on National Accounts Statistics (ACNAS) and Institutional Process
Base year revisions in India are not unilateral government decisions — they go through an Advisory Committee on National Accounts Statistics (ACNAS), a body of external experts and officials that recommends the new base year, data sources, and methodology to MoSPI.
Key Details
- MoSPI constituted a 26-member ACNAS in June 2024, chaired by economist Biswanath Goldar, to guide the choice of new base year and align GDP compilation with other macro indicators (WPI, CPI, IIP).
- The Committee's mandate included examining new data sources such as GST returns, corporate MCA-21 filings, and updated survey data (e.g., the Household Consumption Expenditure Survey, HCES 2023-24) to improve estimation of the informal sector.
- Alignment of GDP, IIP, and CPI base years (all now closer to 2022-23/2023-24) is intended to make cross-referencing between growth, production, and price indicators more consistent for policy use.
The ACNAS recommendation process is the institutional backing MoSPI has cited in describing the base year change as a routine, expert-vetted statistical exercise rather than a discretionary policy decision.
GDP vs GVA and the Double-Deflation Method
Gross Value Added (GVA) measures the value of output net of intermediate consumption, and GDP is derived from GVA by adding taxes on products and subtracting subsidies on products. A related methodological issue in base year revisions is the deflation method used to convert current-price ("nominal") values into constant-price ("real") values.
Key Details
- India has historically used a "single deflation" method (deflating value added directly) for large parts of the economy; more advanced statistical systems increasingly favour "double deflation" (deflating output and inputs separately before subtracting), which the new base year methodology has moved to adopt for eligible sectors, in line with UN System of National Accounts (SNA) 2008 recommendations.
- Double deflation is considered more accurate but requires more granular input-output price data, which is one reason it could only be introduced once newer, richer datasets became available with the base year shift.
- GDP at constant prices is what is reported as "real growth"; GDP at current prices is "nominal growth" — the distinction is central to interpreting any dispute about whether growth figures are being inflated or understated.
The core of the current dispute is a comparison between nominal GDP figures computed under two different base-year series (old 2011-12 series vs new 2022-23 series) for adjoining time periods — MoSPI's position is that nominal or real values from different series are not directly comparable without a proper back-series conversion.
Base-Year-Linked Data Credibility Debates
Statistical revisions of this scale periodically generate public debate about whether growth figures are being over- or under-stated, since a new base year mechanically changes both the levels and the reported growth rates for the same underlying economic activity.
Key Details
- Under the new base-year series, real GDP growth for FY 2025-26 was estimated higher than under the old series' First Advance Estimates, while GDP levels for 2022-23 through 2024-25 were revised down in absolute terms compared to the old series.
- MoSPI has stated that such divergences arise mechanically from the change in reference year, deflators, and data sources, and do not reflect any change in actual underlying economic activity.
- Similar controversies have accompanied earlier revisions internationally and in India (e.g., debate after the 2015 shift to the 2011-12 base year over reported growth rates for 2012-16), showing that base-year-driven growth rate shifts are a recurring feature of statistical methodology, not unique to this revision.
The current dispute over whether reported quarterly growth of 7.8% overstates real momentum is a direct instance of the base-year comparability problem — comparing current-series and old-series figures without adjusting for the change in reference year and methodology.
- New GDP series base year: 2022-23 (previous base year: 2011-12); released 27 February 2026.
- IIP base year updated to 2022-23; CPI base year updated to 2023-24.
- ACNAS: 26 members, constituted June 2024, chaired by Biswanath Goldar.
- Sequence of past GDP base year revisions: 1948-49, 1960-61 (1967), 1970-71 (1978), 1980-81 (1988), 1993-94, 1999-2000, 2004-05, 2011-12 (2015), 2022-23 (2026).
- GDP under the new series is compiled by MoSPI's National Accounts Division; the compiling body has not changed across revisions.
- Disputed figures: nominal GDP for a recent quarter was reported at differing levels (approximately ₹80 lakh crore under the new series vs approximately ₹86 lakh crore under the previous series for the year-ago comparable quarter), which is central to the ongoing comparability dispute. [Unverified — exact quarter and figures should be cross-checked against the official MoSPI press note before use in a factual MCQ context]