OFFICIAL STATISTICS SPECIALLY DESIGNED FOR INDIAN STATISTICAL SERVICE (ISS) AND OTHER GOVERNMENT & PRIVATE SECTOR STATISTICAL EXAMINATIONS
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The Consumer Price Index (CPI) is one of the most important official statistics for understanding changes in the prices faced by households. For ISS aspirants, CPI connects index-number theory, weights, price collection, inflation measurement and monetary-policy concepts. India introduced the CPI 2024 series in February 2026, making the new base and methodology particularly relevant for current examinations.
1. What is the Consumer Price Index?
CPI measures the average change over time in the prices paid by consumers for a representative basket of goods and services. The index is constructed relative to a base period, which is assigned a value of 100.
Why examiners love this topic
CPI brings together price relatives, weighted aggregation, base revision, inflation rates and the distinction between an index level and a rate of change. Questions can be conceptual, numerical or descriptive.
2. CPI 2024: the current series
The current All-India CPI series has 2024=100 as its base. MoSPI's CPI 2024 documentation states that the new basket contains 358 weighted items, classified under 12 divisions, 43 groups, 62 classes and 192 sub-classes using COICOP 2018.
Base
2024=100 for the current CPI series.
Basket
358 weighted items in the CPI 2024 structure.
Classification
COICOP 2018 is used down to the sub-class level.
Exam tip
Do not automatically use 2012=100 when a question asks for the current CPI series. Read the stated reference period carefully.
3. How is CPI constructed?
A weighted price index combines price relatives with expenditure or consumption weights. A simplified Laspeyres form is:
Here Wi is the weight of item or group i and Ii is its price relative or elementary index. In practical official compilation, item-level prices are collected and aggregated through the prescribed hierarchy.
- Remember: an index of 125 means the index level is 25% above the base-period level.
- Inflation: year-on-year inflation compares the current index with the corresponding period of the previous year.
- Base revision: weights and basket composition are updated so the index better reflects current consumption patterns.
4. CPI and inflation: do not confuse the two
CPI is an index level; inflation is a rate of change in prices. If CPI rises from 150 to 156, the percentage increase is:
This distinction is a common source of mistakes in objective and numerical examinations.
5. Rural, Urban and Combined CPI
NSO releases CPI for Rural, Urban and Combined sectors, along with Consumer Food Price Index series. The Combined index is widely used for headline inflation analysis, while separate sectoral indices help study differences in price movements across population groups and locations.
6. Common mistakes students make
- Confusing the CPI base year with the WPI or IIP base year.
- Treating the CPI index level as the inflation rate.
- Forgetting that weights represent relative importance in the consumption basket.
- Using an old basket or classification when the question explicitly refers to the CPI 2024 series.
7. Three important questions
Try each one on your own first, then tap the answer.
What is CPI, and how is it different from inflation?
Show answer
CPI is an index measuring changes in the prices of a representative consumer basket relative to a base period. Inflation is the percentage rate of change in the price level, often measured from the CPI on a year-on-year basis.
A CPI index rises from 150 to 156. Calculate the percentage increase in the index.
Show answer
Percentage increase = (156 − 150) / 150 × 100 = 4%. The result is a rate of change, not the new CPI index level.
Explain the importance of base revision in CPI and discuss major features of the CPI 2024 series.
Show answer
A strong answer should explain why household consumption changes over time, why outdated weights reduce representativeness, and how a revised basket and classification improve measurement. Mention the 2024 base, the 358-item basket and COICOP 2018 classification, while distinguishing the index from inflation.
Key takeaways
- Know the definition, coverage and official source of the indicator before memorising numbers.
- Separate an index level from its percentage growth or inflation rate.
- Read the reference year, population, classification and weights carefully in numerical questions.
- For current-affairs-linked questions, verify the latest official MoSPI or Government of India release before the examination.
Everything on Official Statistics, in one book
This topic is one part of the wider Official Statistics syllabus. The book brings the major concepts together for systematic ISS preparation.
- Indian official statistical system: MoSPI, NSO, NSC and the data they produce
- National accounts, GDP, IIP, price indices and labour statistics
- NSS surveys, sampling designs and data quality concepts
- Written specially for the ISS exam, and useful for other government and private sector statistical exams
- Concept-focused notes to revise quickly before the exam
Official Statistics for ISS and other Government & Private Sector Statistical Examinations