Explain why the base years of macro-economic indices are revised periodically. Discuss the significance of the 2022-23 base revision of the IIP and Index of Core Industries.

A base year is the reference period (index = 100) against which current production is compared [1]. In 2026, India moved GDP, the Index of Industrial Production (IIP) and the Index of Core Industries (ICI) to a common 2022-23 base [1][3]. This brought India's industrial statistics in line with the structure of today's economy.

Why base years are revised periodically

• Structural change: the shares of sectors shift over time, so old weights overstate declining industries [1].
• New products and technology: item baskets go out of date. The new IIP basket has 463 item groups, 120 of them new [1].
• Consistency across indicators: the base should be a stable year aligned with GDP and WPI [1]. The GDP series moved to base 2022-23 in February 2026 [3].
• Policy reliability: current weights give more accurate data for economic analysis and policymaking [1].

Significance of the 2022-23 revision

IIP

• This is the 10th revision, made on the advice of the Technical Advisory Committee (TAC-IIP) [1][2].
• Wider coverage: gas supply, water supply, sewerage, waste management, and minor and rare-earth minerals [1]. Manufacturing carries a weight of 76.062 [7].
• Greater granularity: electricity from renewable and non-renewable sources is shown separately, which helps track the energy transition [1].
• National accounts: the Q1 2026-27 GDP estimates use the new IIP [3].

ICI

• Core sectors go from eight to nine, with Iron Ore added for its importance to industry [4][5].
• Weights are taken from the IIP 2022-23, so the two indices are consistent with each other. Data are available from April 2023 onward [4].
• Steel is now measured by gross production, as in the IIP [5].
• The current weights show what really drives the index. Electricity (30.932) has the largest weight, and the September 2026 growth of 7.9% was led by power [6].

Caveats

• The old and new series are joined using a linking factor of 1.47, so long-run comparisons need care [4].
• Provisional figures change. August 2026 growth was revised from 4.8% to 5.9% [6].
• Electricity, Refinery Products and Steel make up about 71% of the weight, so a few sectors can move the headline [6].

Updating the base year keeps indices accurate as the economy changes. The 2022-23 alignment gives policymakers a consistent and more detailed view of industry and energy. Regular revision, quicker final data and clear linking methods will further strengthen evidence-based policy, in line with SDG 17.18 on timely, reliable data.