GDP Double Deflation & Core Sector 4.8% | CLAT GK

CURRENT AFFAIRS | 22 SEPTEMBER 2026

Two pieces of economic data landed on Monday, 21 September 2026. First, the Ministry of Statistics and Programme Implementation (MoSPI) released its ‘Sources and Methods for Compilation of National Accounts Statistics’ for the new GDP series with 2022–23 as the base year. As reported by The Indian Express on 22 September, the document says the new series uses the ‘double deflation’ method in 28 of the 30 categories of the manufacturing sector, and that work is on to extend it to the remaining two. Second, the Office of the Economic Adviser, Department for Promotion of Industry and Internal Trade (DPIIT), reported that the Index of Core Industries grew 4.8% in August 2026 (provisional), a three-month low, slightly below the 5.0% recorded in July.

Both stories are about the same thing: how India measures its economy. One explains the method behind the headline GDP number; the other is a monthly indicator that feeds into industrial output. For CLAT, which increasingly sets economy-based passages in the General Knowledge section, the vocabulary here — base year, GVA, deflator, core sector, IIP — is exactly what a question will test.

What the ‘Sources and Methods’ document says

The two manufacturing categories where double deflation has not yet been applied are ‘production, processing and preservation of meat, fish, fruit, vegetables, oils and fats’ and ‘manufacture of pharmaceuticals, medicinal chemicals and botanical products’. In both, the share of imported inputs is high, which MoSPI says makes it “challenging” to map input items directly to their elementary, item-level output Producer Price Index (PPI).

The document brings together the concepts, definitions, data sources, methods and compilation practices of the new series. According to the IE report, it contains no new data and draws on the recommendations of three sub-committee reports. It comes seven months after the new series was released, which MoSPI said is the shortest time it has ever taken to publish the full document; previously this has taken up to three years after a new series. The timing had been flagged in advance: MoSPI’s press note on first-quarter GDP, dated 31 August 2026, said ‘Sources and Methods’ was scheduled for release by September 2026.

Single deflation versus double deflation

To get real GVA, both output and inputs must be stripped of price changes. Under single deflation, nominal GVA — or output and inputs together — is divided by one price index. Under double deflation, output is deflated by an output price index and inputs by an input price index, separately, and real GVA is the difference between real output and real intermediate consumption. MoSPI’s Q1 press note describes it exactly so: output and intermediate consumption are “separately deflated using granular Producer Price Indices”.

Why does it matter? Suppose a factory’s output prices rise 2% but its input prices rise 8%. Single deflation, applying one index to both, would misstate real value added, because it assumes input and output prices moved together. Double deflation captures the squeeze on margins. According to the IE report, one of the biggest criticisms of the old 2011–12 series was that MoSPI used double deflation only for agriculture and mining and quarrying; elsewhere, input and output values were deflated by the same number, drawn from the Wholesale Price Index (WPI) and Consumer Price Index (CPI). MoSPI’s February FAQ states that in the new series “single deflation has been completely done away with”: double deflation is used in manufacturing and agriculture, single extrapolation in other sectors, and more than 300 item-level indices are used.

A notable consequence showed up in the first-quarter data. MoSPI’s 31 August press note put real GDP growth at 7.8% in Q1 (April–June) of 2026–27, against 6.9% a year earlier, with nominal GDP growth of 10.3%. In manufacturing, real GVA grew 9.2% while nominal GVA grew only 7.7% — implying a negative implicit price deflator. MoSPI explained that under double deflation the manufacturing deflator can decline, or even turn negative, when input prices (crude petroleum, natural gas, raw materials) rise faster than output prices.

Core sector: 4.8% in August

The Index of Core Industries (ICI) measures the combined and individual production of the economy’s basic industries. According to the Commerce Ministry’s release on 21 September, reported by ANI, the ICI grew 4.8% year-on-year in August 2026 (provisional), compared with 5.0% in July 2026 (final). Cement grew the fastest at 12.5%, followed by electricity (11.6%), iron ore (5.5%), steel (3.4%) and refinery products (2.6%), while coal, natural gas, crude oil and fertilizers contracted. Cumulative growth for April–August 2026 was 4.3%, against 2.4% in the same period last year. The IE noted that six of the nine sectors grew more slowly than in July, and that these six account for over 44% of the index.

Readers used to the phrase “eight core industries” should note the change. On 20 July 2026, DPIIT released a revised ICI with base year 2022–23, replacing the 2011–12 series and adding iron ore as the ninth core industry because of its extensive use in industrial production. According to the official statement, the ICI weights are derived from the Index of Industrial Production (IIP) 2022–23 released by MoSPI and redistributed pro rata to total 100. Steel is now compiled from gross rather than net production, to match the IIP, and only raw coal is retained in the coal sector, with coal middlings and washed coal dropped to avoid double counting. Under the old series, the eight core industries accounted for 40.27% of the weight of items in the IIP. In the new basket, electricity carries the largest weight (30.93%), followed by refinery products (22.57%) and steel (17.58%).

Analysis: better numbers, harder comparisons

The methodological upgrade answers a long-standing critique. Economists had argued that single deflation, especially during periods of volatile commodity prices, could distort measured real growth in manufacturing. By separately deflating inputs and outputs, and by shifting to granular item-level indices, the new series should track real value added more faithfully. The publication of ‘Sources and Methods’ within seven months also matters for credibility: users can now examine exactly how the estimates are built, rather than taking a headline number on trust.

But upgrades create their own puzzles. A negative manufacturing deflator is counter-intuitive to a lay reader and invites the suspicion that real growth is being flattered. MoSPI’s answer is that such outcomes occur in other countries too when supply chains swing, and that double deflation is the internationally recommended approach. The two excluded categories also reveal a practical limit: where imported inputs dominate, matching each input to a domestic price index is difficult. And the WPI used as a deflator still has a 2011–12 base until its own revision is complete, according to MoSPI’s FAQ; comparisons across old and new series will also need the back series, which MoSPI expects by December 2026.

The core-sector reading adds texture. Growth led by cement and electricity points to construction and infrastructure demand, while contraction in coal, crude oil and natural gas weighs on the index. Because the core industries form a large share of the IIP, the ICI is watched as an early signal of industrial output — though, as the weights show, it is a partial one.