Govt considering chain-linking of IIP to keep with global standards

IIP to follow chain-linked index

• India may adopt chain-linked IIP measurement for improved global alignment.
• Annual base year updates for IIP to reflect current industry trends.
• Change may cause more data revisions and loss of additivity in indices.

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India may soon overhaul the way it measures industrial activity, with the government considering a shift in the Index of Industrial Production (IIP) from a fixed-base system to a chain-linked methodology. The move would align India’s industrial statistics more closely with global practices, but it would also introduce more frequent revisions to the data.

At present, the IIP series uses 2011–12 as its base year, with sectoral and industry weights remaining unchanged until a formal rebasing exercise is carried out—often after a long gap. While this approach offers stability and ease of interpretation, it risks becoming less representative as the structure of industry evolves over time.

In a discussion paper released for stakeholder consultation, the Ministry of Statistics and Programme Implementation has outlined the feasibility of adopting a chain-based IIP. Under such a framework, the effective base year would be updated every year. Instead of comparing current output to a single reference year fixed far in the past, a chain-linked index measures changes relative to the immediately preceding year, using more recent weights that better reflect the current industrial landscape.

Moneycontrol had earlier reported that the government was examining a move towards chain-based indices as part of a broader effort to bring India’s statistical system in line with international norms. Many advanced economies already rely on chain-linking for key macroeconomic indicators to better capture structural shifts in production and consumption.

The discussion paper sets out three possible techniques to implement chain-linking for a high-frequency indicator like the monthly IIP: the annual overlap method, the one-month overlap method and the over-the-year method. Each approach differs in how successive series are linked and how continuity is maintained when weights are updated.

The proposed shift, however, comes with trade-offs. One key limitation of chain-linked indices is the loss of additivity—lower-level industry indices will no longer sum exactly to higher-level aggregates, making the data less intuitive for some users. More importantly, the new system would involve multiple revisions to IIP numbers over a two-year period, as more complete information from the national accounts and the Annual Survey of Industries becomes available.