Chapter 4 — Inflation and price measurement

Exam fit: common foundation for SI and Constable. Level: basic to intermediate.

Inflation is a sustained rise in the general price level over time. It is not the same as one product becoming more expensive, and it does not mean that every price rises by the same amount. When the general price level rises, a fixed amount of money buys fewer goods and services on average. The effect on a household depends on its income, savings, debts and spending pattern. A household that spends a large share on food can experience a different cost-of-living change from a household whose budget is dominated by rent or transport.

4.1 Index numbers and percentage change

Index level and inflation rate answer different price questions. | Original explanatory diagram; schematic, not a measured data chart.

A price index summarises price changes for a selected basket relative to a chosen reference period. The base period is assigned a value such as 100. If an index moves from 100 to 106, the index level is 6% higher than its base-period level. If it moves from 120 to 126, the percentage rise over that interval is (126 − 120) / 120 × 100 = 5%, not 6%. Always calculate a change relative to the earlier index level.

The year-on-year inflation rate compares the price index for a month with the index for the same month one year earlier. Month-on-month change compares adjacent months and can be volatile. Annual average inflation compares averages over a year. These measures answer different questions. A question must specify the comparison period; an index level by itself is not an inflation rate.

Worked example. A household price index is 160 in June of Year 2 and 152 in June of Year 1. Year-on-year inflation is (160−152)/152 × 100 = 5.26%, approximately. It is not 8%, the point difference, and not 160%, the current index level. Rounding should be stated when necessary.

4.2 CPI, CFPI and WPI

The Consumer Price Index (CPI) measures changes in prices paid by households for a defined set of consumption goods and services, using a specified basket and weights. It is commonly presented for rural, urban and combined areas and for groups of items. The Consumer Food Price Index (CFPI) focuses on food prices within the published index framework. The Wholesale Price Index (WPI) measures price movements at the wholesale/producer-facing stage for a defined set of commodities and has its own basket and base year. CPI and WPI can move differently because they cover different items, weights and stages of trade.

CPI is used as a broad retail-inflation measure and is the measure named in India's statutory flexible inflation-target framework. A rise in a wholesale input price may eventually affect consumer prices, but the change may be delayed, partly absorbed by firms or offset by changes elsewhere. Do not treat one index as a perfect forecast of the other.

4.3 What “basket” and “weights” mean

A price basket represents goods and services that a statistical system aims to track. Weights represent their relative importance in the measured expenditure pattern. If food has a larger weight in the basket than a rarely purchased item, a given percentage price increase for food contributes more to the overall index, all else equal. Weighting is essential because a simple average of every price would give equal influence to items that households do not purchase equally.

The basket is periodically revised so the index can better represent consumption patterns and available products. MoSPI launched a CPI series with base year 2024=100 in 2026, based on the Household Consumption Expenditure Survey 2023–24 and a revised classification and coverage. This is a methodological update, not simply a renumbering. The 2012-base and 2024-base index levels should not be spliced as though they are one uninterrupted scale. When reading a CPI figure, name its base year, rural/urban/combined scope, reference month and provisional or final status.

The basket includes goods and services, and its design choices affect measured inflation. The index remains a statistical summary, not a personalised cost-of-living calculator for every family. A household can calculate its own spending-weighted change, but it must not call that official CPI unless it follows the official method and basket.

4.4 Inflation, deflation and disinflation

Inflation means the general price level is rising. Deflation means it is falling over a sustained period. Disinflation means inflation is positive but slowing. If inflation falls from 8% to 5%, prices are still rising, only more slowly. A falling inflation rate does not automatically mean that the price level has returned to its earlier level.

Worked timeline. Suppose a fixed basket costs ₹100 at the start of Year 1. It costs ₹110 at the start of Year 2 and ₹115.50 at the start of Year 3. Inflation in Year 2 was 10%; in Year 3 it was 5%. This is disinflation: the rate slowed, while the basket price continued to increase. The basket did not become cheaper.

4.5 Real purchasing power

Real purchasing power describes what money can buy after allowing for price change. A salary increase can be nominally positive but real income may fall if prices rise faster. For a rough personal comparison, subtract the inflation rate from the nominal income growth rate; for greater accuracy use the ratio calculation:

Real growth ≈ [(1 + nominal growth) / (1 + inflation) − 1] × 100

Rates in the formula are decimals. If nominal pay rises 6% while a relevant price measure rises 5%, real growth is (1.06/1.05 − 1) ×100 ≈ 0.95%, close to the one-percentage-point approximation. The CPI may not match the employee's actual basket, so the result is an analytical estimate.

Inflation redistributes purchasing power in ways that depend on contracts and timing. A borrower with a fixed-rate loan may repay in money that has lower purchasing power, while the lender receives lower real value than expected if inflation was unanticipated. A person on a fixed nominal pension may lose purchasing power unless payments adjust. These effects are not automatic in every contract: interest rates, indexation clauses and expectations matter.

4.6 Causes and supply conditions

Demand-pull pressure can emerge when total spending rises faster than the economy's capacity to supply goods and services. Cost-push pressure can arise when production costs—such as fuel, imported inputs, transport or wages—rise. Food prices can respond to weather, harvests, storage, transport, market access and global conditions. These explanations can overlap. A supply shock may raise prices even when household demand is weak.

Expected inflation can influence wage and price setting. If workers and firms expect persistent inflation, they may seek pay or price changes in anticipation. Monetary policy can influence demand and expectations, but it cannot immediately produce a failed monsoon crop or repair a disrupted shipping route. A policy response weighs how persistent price pressure is, how expectations are changing, and the effects of action on output and employment.

4.7 India's inflation target and measurement discipline

Under section 45ZA of the Reserve Bank of India Act, the Central Government, in consultation with RBI, notifies a CPI inflation target for a five-year period. Gazette notification S.O. 1580(E), dated 25 March 2026, sets a 4% target with a 2% lower and 6% upper tolerance level for 1 April 2026 through 31 March 2031. These are the target and tolerance band, not the actual inflation rate in any month. The tolerance band is also not a promise that every individual item or household's costs stay within it.

For exam and media claims, keep these questions together: Which index? Which base? Which month or year? Year-on-year or month-on-month? Rural, urban or combined? Provisional or final? Is the number an index level or a percentage change? Is it an official measure or a personal basket? This compact checklist prevents many errors.

Worked application and examiner distinction

Two households can experience different cost pressures even when a national CPI rate is correct. A rural household may spend a larger share on food, while a salaried urban household may spend more on rent and transport. The index uses a defined representative basket and weights; it does not claim that every household buys the same quantities. A personal inflation rate could be calculated from that household's own basket, but it should not be mistaken for the official CPI.

If a basket costs ₹2,000 in the base period and ₹2,100 in the later period, the index is 105 when the base equals 100. The price-level increase is 5%, not “inflation of 105%.” If the next period's index is 108, inflation between those two periods is `(108−105)/105 × 100`, or about 2.86%. The inflation rate slowed, but the measured price level still rose. Disinflation is a slowing rate of increase; deflation is a decline in the general price level under the defined index.

This edition's source register identifies the 2024-base CPI series and the notification of the inflation target for 2026–31. Do not compare index levels across different base series without a compatible linking method. For any current monthly rate, consult the exact release and record whether it is provisional and which reference month it covers.

Second worked calculation and interpretation

An index moves from 100 to 108, then to 111.24. First-period inflation is 8%. Second-period inflation is 3%, because 3.24 divided by 108 equals 3%. The cumulative rise from 100 to 111.24 is 11.24%, not 11%. Compounding matters. A slowing inflation rate does not mean the basket became cheaper; the index is higher than before.

Suppose another basket has a different base index, 100 in a later year, and a value of 105. The numbers 111.24 and 105 cannot be compared as relative price levels unless the series are linked or re-referenced under a valid method. Rates may be compared when both are calculated consistently for their own series and periods, but series definitions still matter. This is why the edition labels CPI bases and advises checking release notes.

Applied examiner workshop

Suppose an index is 120 in April and 126 in May. Month-on-month inflation is `(126−120)/120 × 100 = 5%`. If the year-ago May index was 120, year-on-year inflation is also 5% in this hypothetical example, but only by coincidence. In a real series the comparison bases can differ. The index's reference period and comparison convention must be named in the stem or release.

If food prices rise but fuel and some service prices fall, the overall index depends on the basket weights and changes in all covered categories. The contribution of an item is not simply its price change; weight and aggregation method matter. A high-weight category with a modest rise can contribute more than a low-weight category with a large rise. Category inflation can differ from headline inflation.

The inflation-target notification for 2026–31 specifies a target and tolerance band; that framework is not a monthly forecast or promise that actual CPI will stay exactly at target. For exam questions, distinguish the target, actual inflation, forecast, index level and inflation rate. If a question asks for the current official rate, use a dated release. Do not state an undated rate as a stable fact.

Chapter recall

• Inflation is a sustained rise in the general price level; one price increase is not sufficient to establish it.
• An index level and a percentage change are different.
• CPI, CFPI and WPI use different baskets, weights and price stages.
• India's CPI base 2024=100 series began in 2026; do not splice it with the 2012-base scale without an official linking method.
• Disinflation means a slower positive rise, not falling prices.
• A nominal income gain can be partly or wholly eroded by inflation.
• The 2026–31 statutory CPI inflation target is 4% with a 2–6% tolerance band; actual monthly inflation is a separate observation.

Quick retrieval

1. An index rises from 125 to 130. What is the percentage change?

2. If inflation falls from 7% to 4%, are prices necessarily lower than before?

3. Why does a basket use weights?

4. Why should the 2012-base and 2024-base CPI levels not be joined casually?

5. What is the difference between a target and a recorded inflation rate?

Chapter 4 practice MCQs

1. Inflation is best described as:

• A. a one-time increase in a household's income
• B. any single item's price increase
• C. a sustained rise in the general price level
• D. a decline in every product's output

Answer: C. Inflation concerns a general price-level rise over time. A single relative price can rise without the overall index increasing at the same rate.

2. A price index moves from 120 to 126. The percentage increase is:

• A. 5%
• B. 6%
• C. 26%
• D. 0.5%

Answer: A. The increase is 6 relative to 120: 6/120 × 100 = 5%.

3. An index has a base value of 100 and later reaches 108. The later index level is:

• A. an inflation rate of 108% for every month
• B. 8% above the base-period level
• C. eight index points below the base
• D. proof that every item rose 8%

Answer: B. The index level is eight points above 100, or 8% higher than that base value. It does not state that every item rose identically or specify a monthly rate.

4. Year-on-year inflation for a month compares the index with:

• A. only the immediately previous day
• B. the population in the previous census
• C. the same month one year earlier
• D. the annual budget estimate

Answer: C. The year-on-year comparison uses the corresponding month in the previous year. Month-on-month inflation uses a different comparison.

5. If inflation falls from 8% to 5% while remaining positive, this is:

• A. deflation
• B. a fall in the price level
• C. hyperinflation by definition
• D. disinflation

Answer: D. The rate of increase has slowed but prices are still rising. Deflation would mean a sustained decline in the general price level.

6. Which index is designed to track consumer prices for a specified household-consumption basket?

• A. CPI
• B. GDP at current prices
• C. fiscal deficit
• D. exchange-rate index

Answer: A. CPI follows a defined household consumption basket and weights. The other measures answer different questions.

7. The Consumer Food Price Index focuses on:

• A. food-price movement within the published index framework
• B. all government borrowing
• C. wholesale prices of machinery alone
• D. every service and asset price equally

Answer: A. CFPI is the food-focused measure. Its exact coverage and series are defined by MoSPI.

8. CPI and WPI may move differently because they:

• A. are measures of population growth
• B. are the same index in every series
• C. both measure only wages
• D. differ in coverage, basket weights and price stage

Answer: D. They track different baskets and price stages. Changes need not be identical or simultaneous.

9. In 2026 MoSPI introduced which CPI base series?

• A. 2024=100
• B. 1970=100
• C. 2011=100
• D. 2030=100

Answer: A. MoSPI launched the 2024=100 CPI series in 2026. State the base year when quoting an index.

10. A CPI basket uses expenditure weights mainly to:

• A. replace price observations with GDP growth
• B. give every listed item exactly equal influence
• C. remove rural households from the index
• D. reflect the relative importance of items in measured household consumption

Answer: D. Weights let items with different expenditure importance contribute appropriately to the composite measure.

11. A 2012-base index equals 150 and a 2024-base index equals 110 for a later period. Without an official linking procedure, one should:

• A. conclude that prices fell by 40%
• B. avoid treating the two levels as one continuous scale
• C. subtract the index values and call it inflation
• D. assume the new series counts only urban prices

Answer: B. The base and method may differ. Compare within compatible series or use an official linking method.

12. A household basket costs ₹200 at one date and ₹210 one year later. The simple inflation rate for that basket is:

• A. 105%
• B. 10%
• C. 0.5%
• D. 5%

Answer: D. The increase is ₹10 relative to the original ₹200: 10/200 × 100 = 5%.

13. Nominal salary rises by 4%, while a relevant price index rises by 6%. The employee's approximate real purchasing power:

• A. falls
• B. rises by 10%
• C. is unchanged exactly
• D. cannot be affected by prices

Answer: A. Prices rose faster than nominal salary, so the salary buys less under the relevant basket. The precise personal effect depends on the employee's actual spending pattern.

14. A rough real-growth approximation is nominal growth minus inflation when:

• A. the base period is unknown
• B. the rates are modest and the comparison is clearly approximate
• C. the two rates refer to different decades
• D. the index level is treated as a percentage rate

Answer: B. Subtraction is a useful approximation for small rates. Exact calculation uses a ratio and a compatible deflator/index.

15. Which is a demand-pull explanation of inflation?

• A. a transport bottleneck disrupts supply
• B. Aggregate spending rises faster than productive supply can respond
• C. imported fuel becomes more expensive
• D. a storm damages a crop

Answer: B. Demand-pull pressure arises when spending exceeds available supply capacity. The other options are examples of supply-side or cost pressures.

16. A harvest shortfall raises food prices even while overall demand is weak. This is most directly an example of:

• A. an increase in money's purchasing power
• B. a supply shock
• C. a tax refund
• D. a decline in all prices

Answer: B. A harvest loss reduces supply and can raise prices. Inflation need not originate from strong demand.

17. The notified CPI inflation target for 1 April 2026 to 31 March 2031 is:

• A. 4%, with a 2% lower and 6% upper tolerance level
• B. 2%, with a 4% upper and 6% lower level
• C. 6% with no tolerance range
• D. a fixed monthly rate of 4%

Answer: A. Gazette notification S.O. 1580(E) sets the 4% target and the 2–6% tolerance levels for the stated five-year period. It is not an actual monthly reading.

18. The tolerance band is best understood as:

• A. a tax bracket
• B. a guarantee that each household's basket changes within that range
• C. the lower and upper limits around the notified target for the framework
• D. a forecast for every commodity price

Answer: C. The band is part of the statutory inflation-target framework. Individual prices and household experiences can differ.

19. A fall in the inflation rate from 6% to 3% means, under positive inflation:

• A. CPI has become equal to WPI
• B. prices have returned to their level from before the earlier increase
• C. every price is falling by 3%
• D. prices are still rising, but more slowly than before

Answer: D. Positive inflation means the measured price level continues to rise. A lower rate does not reverse previous increases.

20. Which information is essential when a report quotes “CPI inflation was 3%”?

• A. The number of banks in the district
• B. Only the newspaper's headline colour
• C. Base series, reference period, comparison method and geographic scope
• D. The author’s preferred basket

Answer: C. A useful CPI rate should be tied to the series/base, period, comparison (such as year-on-year) and scope (rural, urban or combined).

21. A 10% rise in a wholesale input cost must lead to a 10% rise in CPI because:

• A. this statement is false; pass-through depends on costs, margins, substitution and timing
• B. CPI and WPI are identical
• C. every firm immediately doubles its price
• D. consumer demand is irrelevant

Answer: A. Wholesale-cost changes may pass through partially, with a lag or not at all. Other costs, margins, demand and policy conditions matter.

22. Which statement about inflation and purchasing power is correct?

• A. A sustained rise in the general price level reduces the amount a fixed nominal sum can buy on average
• B. inflation raises every household's real income automatically
• C. inflation is the same as a rise in one asset price
• D. the CPI measures only national output

Answer: A. Inflation reduces the purchasing power of a fixed nominal amount on average. Individual households' experiences depend on their baskets and incomes.

23. A basket costs ₹100, then ₹110, then ₹115.50 across two consecutive years. The second year's inflation rate is:

• A. 5%
• B. 10%
• C. 15.5%
• D. 0.5%

Answer: A. The second-year change is ₹5.50 divided by the previous ₹110, which equals 5%. The price level is still higher than at the start.

24. Which statement best explains why official inflation measures may be revised or re-based?

• A. Re-basing means that every past price is erased
• B. Consumption patterns and statistical methods can change, requiring updated baskets or weights
• C. Prices are not observed by statistical agencies
• D. A new index guarantees lower measured inflation

Answer: B. Basket, weights, classification and methods may need updates as consumption changes. Re-basing does not guarantee that inflation rises or falls.