The revision of the Index of Core Industries base year from 2011-12 to 2022-23 is the direct sequel to the wholesale price index revision, and it carries something the earlier story did not: a published linking factor.
If you read yesterday’s article on the WPI base year 2022-23, you already know why base years are revised. This one shows you what happens next, when a statistical agency has to make an old series and a new series comparable. That is splicing, and it is in your Statistics Paper III syllabus.
Short answer. The Office of the Economic Adviser has released the first provisional Index of Core Industries on a new 2022-23 base year, replacing 2011-12. Iron ore has been added, taking the count from eight core industries to nine. A linking factor of 1.47 has been published to make the old and new series comparable, and the index has been implemented retrospectively from April 2023 with a back series.
What the Index of Core Industries Measures
The Index of Core Industries measures the combined and individual production performance of India’s key infrastructure industries.
It matters beyond itself, because these industries carry a substantial weight inside the Index of Industrial Production. When core industries slow, the broader industrial index follows.
That is why the ICI is watched as a leading indicator of industrial activity, and why a revision to it ripples outward.
What Changed in the Index of Core Industries Base Year Revision
| Feature | Old series | New series |
|---|---|---|
| Base year | 2011-12 | 2022-23 |
| Number of industries | Eight | Nine |
| Industry added | Not applicable | Iron ore |
| Linking factor | Not applicable | 1.47 |
| Implementation | Retrospective from April 2023 | |
| Back series | Published |
The nine industries
Coal, crude oil, natural gas, refinery products, fertilisers, steel, cement, electricity, and now iron ore.
For years this was called the Eight Core Industries and examined under that name. It is now nine. If you memorised the list from an older source, update it, because naming eight in 2027 is a dated answer.
Why iron ore was added
Iron ore is an input into steel, which was already in the index. Adding the raw material alongside the finished product gives a fuller picture of the production chain and captures activity earlier in the cycle.
The Linking Factor Is the Part Worth Studying
Here is why this topic earns its place ahead of bigger news stories.
A linking factor is the number used to splice two index series onto a common base, so that values calculated on an old base can be expressed on the new one.
A published linking factor of 1.47 means the agency has told you exactly how to convert. That is not a press release detail. That is index number theory, published by the government, with a number attached.
Where this sits in your syllabus
Statistics Paper III, Applied Statistics, covers index numbers, including base shifting, splicing and deflating, and the tests for index numbers.
| Syllabus concept | Its live example in this story |
|---|---|
| Base shifting | 2011-12 moved to 2022-23 |
| Splicing | The linking factor of 1.47 |
| Chain base and fixed base | The back series from April 2023 |
| Composition of index numbers | Eight industries becoming nine |
Almost nobody preparing for this examination makes that connection. A candidate who does, in an interview, is demonstrating that they read official statistics as a statistician rather than as a news reader.
The ISS syllabus, paper by paper
Why Retrospective Implementation Matters
The new index was implemented retrospectively from April 2023, with a back series published.
That decision solves a real problem. A new index starting today would give you no history, so no growth rate could be calculated for the first year and no comparison with the past would be possible.
Publishing a back series means the new index has a history from the moment it launches. It is a small operational choice with a large analytical consequence, and noting it in an answer shows you understand how statistical systems actually work.
The Bigger Story: Coordinated Base Year Revision
The Index of Core Industries is the second index in this series to move to 2022-23, after the Wholesale Price Index.
Coordinated revision is deliberate. Indices sharing a base year can be compared directly. Indices on different base years cannot, without exactly the kind of linking factor published here.
WPI base year 2022-23 and the Producer Price Index
How This Is Asked in the UPSC ISS Paper
General Studies, Question 3, carries an Economy part on current economic developments almost every year, and industrial performance indicators sit squarely in it.
Statistics Paper II, Official Statistics, covers the Indian Statistical System and its major data collections.
Statistics Paper III, Applied Statistics, covers index numbers directly.
Official Statistics for UPSC ISS · Check how often index numbers have been asked
Model answer skeleton, about 200 words
- Opening. The Index of Core Industries base year moves from 2011-12 to 2022-23, released by the Office of the Economic Adviser.
- What the index measures. Key infrastructure industries, and their weight inside the Index of Industrial Production.
- What changed. Eight industries to nine with iron ore added, a linking factor of 1.47, retrospective implementation from April 2023 with a back series.
- Why revision was needed. The basket and weights go stale as the economy changes.
- The statistical point. The linking factor is splicing. Base shifting and splicing are standard index number operations, here applied by a government agency.
- Closing. Coordinated base year revision across indices preserves comparability, which is what makes a statistical system usable rather than merely current.
Two Mistakes to Avoid
Still calling them the Eight Core Industries. It is nine. This is the most likely single error on this topic, because every older source says eight.
Describing the revision without explaining the linking factor. The linking factor is the only part of this story that a statistics candidate can explain better than anyone else. Skipping it wastes your advantage.
Frequently Asked Questions
What is the new Index of Core Industries base year?
2022-23, replacing 2011-12. The revised index has been implemented retrospectively from April 2023 with a published back series.
How many core industries are there now?
Nine. Iron ore has been added to the previous eight: coal, crude oil, natural gas, refinery products, fertilisers, steel, cement and electricity.
What is the linking factor of 1.47?
A linking factor is the number used to splice two index series onto a common base, so that values calculated on the old base can be expressed on the new one. The Office of the Economic Adviser has published 1.47 for this purpose.
What is splicing in index numbers?
Splicing is the process of joining two index series with different base years into one continuous series, using a linking factor. It is part of the index numbers topic in Applied Statistics.
Who publishes the Index of Core Industries?
The Office of the Economic Adviser, under the Department for Promotion of Industry and Internal Trade.
Why does the Index of Core Industries matter?
These industries carry a substantial weight within the Index of Industrial Production, so the core industries index is watched as a leading indicator of broader industrial activity.
Why was the index implemented retrospectively?
So that the new series has a history from launch. A new index beginning today would allow no growth rate calculation and no comparison with past periods until a full year had passed.
What Comes Next
Two indices revised, one linking factor published. The next article covers the day the statistical system celebrates itself, and the progress report it released alongside.
Next: National Statistics Day 2026, explained for UPSC ISS
Practice. Improve. Repeat.
Sources
Office of the Economic Adviser (eaindustry.nic.in), Department for Promotion of Industry and Internal Trade, Press Information Bureau (pib.gov.in).
