4 min readSep 3, 2026 06:30 PM IST First published on: Sep 3, 2026 at 06:30 PM ISTA former finance secretary recently challenged the official Q1 FY2026-27 growth figures of 7.8 per cent in real terms and 10.3 per cent in nominal terms, suggesting that the corresponding growth rates were actually around 2.6 per cent and below 2.5 per cent. His calculation, however, has a fatal methodological flaw: It uses the old-series nominal GDP of Rs 86.05 lakh crore for Q1 FY2025-26 as the denominator against the new-series figure of approximately Rs 80 lakh crore. One cannot calculate a meaningful growth rate by mixing two incompatible statistical series. On this point, the Ministry of Statistics and Programme Implementation (MoSPI) is right. But that does not dispose of the more substantive question.Under the old 2011-12-base-year series, nominal GDP for Q1 FY2025-26 was officially estimated at Rs 86.05 lakh crore and Q2 at Rs 85.25 lakh crore — a first-half total of Rs 171.30 lakh crore. Under the new 2022-23-base-year series, Q1 was revised to roughly Rs 80 lakh crore and Q2 also to approximately Rs 80 lakh crore. The first-half estimate has fallen by around Rs 11 lakh crore, or about 6.5 per cent. This is not a rounding error. The most striking feature is that this enormous revision is concentrated in the first two quarters.AdvertisementThere is an obvious reason this deserves scrutiny. The old series was discontinued before comparable official Q3 and Q4 estimates for 2025-26 were published. So, there is no complete old-series annual estimate against which the new series can be reconciled quarter by quarter. MoSPI should open that window.Also Read | Controversy over GDP numbers is unwarrantedA change of base year is not a cosmetic exercise. A new national-accounts series incorporates new data sources, wider coverage, improved indicators, methodological changes and revised approaches to measuring prices and volumes. It can — and should — change historical estimates when better information becomes available. But there is a crucial distinction that must not be lost in the debate. Changing the base year primarily changes the measurement of real GDP. Nominal GDP is measured at current prices. Therefore, the fact that the base year has changed from 2011-12 to 2022-23 does not, by itself, explain the reduction of approximately. There may well be legitimate statistical reasons for the revision. But they need to be quantified.MoSPI should publish a simple reconciliation bridge showing, in rupees, how the old estimate became the new estimate. For both Q1 and Q2, the public should be told how much of the revision is attributable to: revised source data; changes in sectoral coverage; methodological changes; revised estimates of taxes and subsidies; changes in price indices and deflators; and other statistical adjustments.AdvertisementThe same exercise should be undertaken for GVA. If manufacturing, trade, financial services, agriculture, or any other major component accounts for a significant part of the revision, the numbers should show it. That would settle the argument effectively. It is equally important not to fall into the opposite trap. A downward revision of GDP is not a loss of GDP. The economy has not suddenly become Rs 11 lakh crore smaller. Better data can lead to downward revisions.Over three years from 2022-23 to 2025-26, nominal GDP increased by about 32.8 per cent under the old series and about 32.3 per cent under the new series. The cumulative real GDP increase is also broadly comparable, though somewhat lower under the new methodology.you may likeOfficial statistics deserve confidence — but confidence is strengthened by transparency, not demanded in its absence. It is wrong to calculate current growth by combining an old-series denominator with a new-series numerator. But it is equally unsatisfactory to dismiss questions about a massive revision simply by invoking “change of base year”.Statistics are not credible merely because they are official. They become credible when an independent reader can understand, reproduce and interrogate the numbers.The writer retired as a senior IAS officer. Views are personal