Former chief statistician Pronab Sen seeks two GDP series with old, new bases for five years

New Delhi: Former chief statistician Pronab Sen said the National Statistics Office (NSO) should come out with two separate gross domestic product series with the old and new base for at least five years, insisting that double deflation is the correct way only if data on both input and output prices are available.

"GDP revision is something which is normal when the base change happens. The correction to GDP happened last year and therefore, the quarterly figures were adjusted accordingly but the correction that happened was larger," Sen said.

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India launched a new GDP series in February this year with 2022-23 as the base year, updating it from 2011-12. It released data up to FY25 under the new series.

Sen's statement assumes significance in the wake of former finance secretary Subhash Garg questioning the government's reported 7.8% real GDP growth for the April-June quarter of FY27.

Garg said GDP for the year-earlier quarter had been revised to about ₹80 lakh crore from around ₹86 lakh crore, and without the benefit of base effect from this revision, the nominal growth would have been around 2.6%.

The Ministry of Statistics and Programme Implementation, meanwhile, said as per the past practice for calculation of back series in India, estimates were recalculated using revised methodology of the new series till the immediate preceding base and spliced at the disaggregated level, thereafter, till 1950-51.

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"A judicious approach combining splicing and recalculation, aligned with the international best practice, will be used...back series is expected to be released by December 2026," it said in a statement on February 27.

On the deflator front, Sen said the use of Producer Price Indices (PPIs) and double deflation needed to be looked at.

"We are not sure if the database is robust enough for double deflation because we were trying to get PPI for a long time but were unsuccessful as producers don't like to share what they charge their customers. Pricing is important, otherwise their competition will get to know what they charge their customers. Therefore, we can never get producers' price because of non-response," he said. Double deflation, Sen explained, needed the price of both the final product and every input as compared to single deflation where only the final product price is needed.