Inflation and Index Numbers: CPI, WPI, IIP and the Deflator

1. Index numbers: meaning and construction

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What an index number is

• An index number is a statistical tool. It measures the average change in a group of related variables between two situations, such as two years or two places. It is usually written as a percentage.
• The comparison period is the base period, and its value is set at 100. An index of 250 means the value is 2.5 times the base value.
• A price index measures changes in the prices of chosen goods. Price indices are the most widely used kind.
• A quantity index measures changes in physical volume, such as production, construction or employment. The Index of Industrial Production is one example.
• Why we need it (Class 11, Index Numbers):
• An industrial worker earned ₹1,000 in 1982 and earns ₹12,000 today. Is the worker 12 times better off? You cannot say until you know how much prices rose.
• How is inflation measured? You need one number that sums up thousands of different price changes.

Worked data (Class 11, Index Numbers, Examples 1–3)

Commodity	p₀	q₀	p₁	q₁	Price relative (p₁/p₀×100)	Weight W (base expenditure share)
A	2	10	4	5	200	40
B	5	12	6	10	120	30
C	4	20	5	15	125	20
D	2	15	3	10	150	10

Aggregative methods

• Simple aggregative price index = ΣP₁/ΣP₀ × 100 = (4+6+5+3)/(2+5+4+2) × 100 = 18/13 × 100 = 138.5, which means prices rose 38.5%.
• It has limited use because prices are in different units (per kg, per litre).

• It is unweighted: every item counts equally, even though food takes up a much bigger share of spending than salt.

• A weighted index takes the relative importance of items into account through weights, such as quantities or expenditure shares.

• A weighted aggregative price index prices a fixed basket in both periods: Σp₁q/Σp₀q × 100. Because the basket does not change, any change in its value comes only from prices.
• Laspeyres price index uses base-period quantities: Σp₁q₀/Σp₀q₀ × 100 = 257/190 × 100 = 135.3.
• (NCERT error: the denominator is printed as 100. The correct figure is 20+60+80+30 = 190.)

• It asks: if the base basket cost ₹100 then, what does the same basket cost now?

• Paasche price index uses current-period quantities: Σp₁q₁/Σp₀q₁ × 100 = 185/140 × 100 = 132.1.

• It asks the same question for today's basket.

• Substitution bias: consumers shift away from goods whose prices have risen fastest. Laspeyres ignores that shift, so it tends to overstate the rise in the cost of living. Paasche tends to understate it. Fisher's ideal index is the geometric mean of the two (beyond NCERT).

Method of averaging relatives

• Price relative = (p₁/p₀) × 100. It is the index for a single good.
• Method of averaging relatives: take the simple average of the relatives, (1/n) Σ(p₁/p₀) × 100 = ¼(2 + 1.2 + 1.25 + 1.5) × 100 = 149.
• Weighted index of price relatives = ΣWR/ΣW. The weights are usually base-period expenditure shares.
• (40×200 + 30×120 + 20×125 + 10×150)/100 = 15,600/100 = 156, a 56% rise.

• It is higher than the unweighted 149 because item A, the heaviest item (weight 40), doubled in price.

• Why base-period weights are preferred: recalculating weights every year is inconvenient, and indices with changing weights value different baskets, so they are not strictly comparable.

2. Issues in construction: base year, representativeness and base revision

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Class 11, Index Numbers: checklist for building an index

• Clear purpose. A volume index is the wrong tool when you need a value index.
• Representative items. The basket must match the reference group. A petrol price rise barely touches poor agricultural labourers, so petrol should carry little weight in their index.
• A "normal" base year. The base year is the year whose prices anchor the comparison. It should:
• avoid extreme years such as droughts, wars or booms;

• not be too distant. Comparing 1993 with 2005 is meaningful; comparing 1960 with 2005 is not, because many items in the 1960 basket have since vanished.

• Choice of formula. It depends on the question. Laspeyres and Paasche differ only in their weights.

• Reliable data. Poor data mislead. Use primary data, or the most reliable secondary source.

Base-year revision

• Base-year revision means periodically shifting an index's (or the national accounts') base year. This keeps baskets, weights and data sources in line with current consumption and production.
• Why revise:
• Consumption patterns change: food's share falls as incomes rise, and services, mobile data and packaged foods grow.
• Items drop out and new ones appear.

• Better surveys and data sources become available.

• Splicing: old and new series are joined with a linking factor so that long-run comparison stays possible. For example, the CPI-IW 2001 → 2016 linking factor was 2.88. DA calculations rely on these links.

India's base-revision cycle

Index	Compiler	NCERT base	Revised base
CPI-IW	Labour Bureau	2001	2016 (released 2020)
CPI Rural/Urban/Combined	NSO (MoSPI)	2012	2024; new series from 2026 (verify current)
WPI	OEA-DPIIT	2011-12	2022-23 (verify current)
IIP	NSO (MoSPI)	2011-12	2022-23 (verify current)
GDP	NSO (MoSPI)	2011-12	2022-23 (verify current)
CPI-AL/RL	Labour Bureau	1986-87	newer base (verify current)

• Aim: align the bases of GDP, CPI, WPI and IIP so that real growth, deflators and inflation are measured on a consistent footing, and revise them every few years rather than every decade or more.

3. The consumer price index family in India

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What the CPI measures

• The Consumer Price Index (CPI) is a cost-of-living index of retail prices for a reference group of consumers. It is the current cost of a fixed basket as a percentage of that basket's base-year cost.
• Reading it: "CPI-IW (2001 = 100) is 277 in December 2014" means a worker who spent ₹100 on a typical basket in 2001 needs ₹277 for the same basket in December 2014. What matters is whether the worker can buy the basket, not whether they actually do.
• Basket of commodities: a fixed, representative set of goods and services. Its weights come from household consumption expenditure surveys.
• Retail prices are what consumers pay. They are collected by the NSO. Wholesale prices are bulk prices. The two differ by traders' margins (Class 12, National Income Accounting).
• Class 12, National Income Accounting example: a consumer buys 90 kg of rice and 5 pieces of cloth.
• In 2000, rice cost ₹10/kg and cloth ₹100/piece, so the basket cost ₹900 + ₹500 = ₹1,400.
• In 2005, rice cost ₹15 and cloth ₹120, so the basket cost ₹1,350 + ₹600 = ₹1,950.
• CPI = 1,950/1,400 × 100 = 139.29.

Construction example (Class 11, Index Numbers, Table 7.4)

Item	W	p₀	p₁	R	WR
Food	35	150	145	96.67	3,383.45
Fuel	10	25	23	92.00	920.00
Cloth	20	75	65	86.67	1,733.40
Rent	15	30	30	100.00	1,500.00
Misc.	20	40	45	112.50	2,250.00
Total	100				9,786.85

• CPI = ΣWR/ΣW = 9,786.85/100 = 97.86, so the cost of living fell 2.14%.
• (NCERT slip: the food WR is printed as 3,883.45. The correct value is 35 × 96.67 = 3,383.45, and only this value gives the printed total of 9,786.85.)
• Exercise logic (Class 11, Index Numbers, Q18): CPI = 125, food index = 120, other items = 135. Solve 120w + 135(1−w) = 125, so w = 2/3. Food therefore has about 66.7% of the weight.

Variants, compilers and bases

• CPI for Industrial Workers (CPI-IW): compiled monthly by the Labour Bureau. Base 2016 since 2020 (NCERT outdated: 2001 = 100; May 2017 value 278). It is used to revise the DA of government employees and industrial wages. Food has the highest weight (NCERT exercise).
• CPI for Agricultural Labourers (CPI-AL): Labour Bureau. It is used to revise minimum wages in agriculture. NCERT gives 1986-87 = 100 (May 2017 value 872); a newer base is being introduced (verify current).
• CPI for Rural Labourers (CPI-RL): Labour Bureau. Covers agricultural and non-agricultural rural labourers and is used for rural minimum wages. NCERT gives 1986-87 = 100 (May 2017 value 878); newer base (verify current).
• CPI for Urban Non-Manual Employees (CPI-UNME): formerly compiled by the CSO. It has been discontinued and replaced by CPI-Urban.
• CPI-Rural and CPI-Urban: compiled monthly by the NSO (MoSPI), also state-wise. NCERT gives 2012 = 100 (May 2017: Rural 133.3, Urban 129.3). The new base is 2024 (verify current).
• CPI-Combined (CPI-C): combines Rural and Urban (May 2017: 131.4). Its year-on-year change is India's headline retail inflation and the RBI's main measure and target.

CPI-C weights, 2012 series (2011-12 CES, 68th NSS round, MMRP; Economic Survey 2014-15)

Group	Weight
Food and beverages	45.86
Pan, tobacco and intoxicants	2.38
Clothing and footwear	6.53
Housing (urban only)	10.07
Fuel and light	6.84
Miscellaneous	28.32

• The new 2024-base series draws its weights from HCES 2022-24, and food's share is lower (verify current).
• Consumer Food Price Index (CFPI): compiled by the NSO for rural, urban and combined India. It is the food and beverages group minus non-alcoholic beverages and prepared meals, snacks and sweets.
• (NCERT error: it says "alcoholic beverages". Alcoholic beverages sit in the pan-tobacco-intoxicants group, not in food.)

• Its weight in the 2012 CPI-C was about 39.

• Why separate CPIs? Baskets differ by group. A labourer's basket is mostly food. A senior official's includes cars and travel. CPI-UNME could not represent the President of India's cost of living, because that basket is not typical of urban non-manual employees.

4. WPI, PPI, and headline vs core inflation

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Wholesale Price Index

• The Wholesale Price Index (WPI) tracks the prices at which goods, including raw materials and semi-finished goods, are traded in bulk. It measures the general price level with no reference consumer group.
• It covers goods only. Services such as barber charges or repairs are excluded.
• It is compiled by the Office of the Economic Adviser (OEA), DPIIT. Base 2011-12 = 100 (NCERT; May 2017 value 112.8). Revision to 2022-23 (verify current).
• Reading it: "WPI (2004-05 base) = 253 in October 2014" means the general price level rose 153% over that period.
• WPI major groups (2011-12 series):

Group	Weight
Primary articles	22.62
Fuel and power	13.15
Manufactured products	64.23
All commodities	100.00

• WPI Food Index = food articles (from primary articles) + food products (from manufactured products). Its weight is 24.23, about a quarter of the WPI.
• Producer Price Index (PPI): measures the average prices received by domestic producers, excluding taxes, trade margins and transport. The USA and many other countries use a PPI instead of a WPI (Class 12, National Income Accounting). India has worked on moving from the WPI to a PPI that also covers services (verify current).

Headline vs core

• Headline inflation is inflation on the full index, including volatile food and fuel. In India it now means CPI-C inflation.

• (NCERT outdated: it calls "all-commodities WPI inflation" headline and gives a weekly WPI formula. India shifted to CPI after the Urjit Patel Committee (2014). The weekly WPI series has ended; WPI is now monthly.)

• Core inflation excludes volatile food and fuel, so it shows underlying, demand-driven pressure. It is now measured on the CPI excluding food and fuel.

• (NCERT outdated: WPI non-food manufactured products, about 55% of the WPI.)

Why WPI and CPI diverge

Feature	CPI-C	WPI
Prices	Retail	Wholesale (bulk)
Services	Included (housing, health, education, transport)	Excluded
Heaviest part	Food (45.86 in 2012 series)	Manufactured products (64.23)
Sensitive to	Monsoon, vegetables, pulses	Global commodities, crude oil, metals
Compiler	NSO (MoSPI)	OEA-DPIIT

• Examples:
• In 2022, WPI inflation reached double digits (commodity and oil shock) while CPI stayed around 7%.

• There have been negative WPI episodes (for example, 2015–16 and mid-2023) while CPI stayed positive because food and services kept rising.

• What the gap signals: when WPI runs ahead, cost pressure may later pass through to retail prices. When CPI runs ahead, food or services are the driver.

5. Quantity indices: IIP, its classifications and other indices

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Index of Industrial Production

• The Index of Industrial Production (IIP) is a monthly quantity index compiled by the NSO (MoSPI). It measures short-term changes in the volume of industrial output.
• Formula: a weighted arithmetic mean of quantity relatives, with weights set by value added in the base year, using the Laspeyres formula:

• IIP₀₁ = Σ(q₁ᵢ Wᵢ)/ΣWᵢ × 100, where q₁ᵢ is the quantity relative of good i.

• Base: 2011-12 = 100 from April 2017 (NCERT). Revision to 2022-23 (verify current).

• Why frequent base changes? Every year many items stop being made or become unimportant, and new items appear.

Weights (2011-12 series, MoSPI 2016-17)

Sector	Weight		Use-based group	Weight
Mining	14.4		Primary goods	34.1
Manufacturing	77.6		Capital goods	8.2
Electricity	8.0		Intermediate goods	17.2
			Infrastructure/construction goods	12.3
			Consumer durables	12.8
			Consumer non-durables	15.3

• Use-based classification of IIP: groups items by end use. Primary goods have the largest weight (about 34%). By sector, manufacturing is largest.
• How to read the groups:
• Consumer durables vs non-durables act as a demand signal. Weak non-durables point to rural or mass-consumption stress. Weak durables point to weak discretionary demand.
• Capital goods act as an investment signal, showing whether firms are adding capacity.
• Infrastructure/construction goods reflect public capex and housing.

Eight core industries

• The eight core industries are coal, crude oil, natural gas, refinery products, fertilisers, steel, cement and electricity. Together they carry 40.27% of the IIP.
• Their index is compiled by OEA-DPIIT and released earlier than the IIP, so it serves as a lead indicator (detail in industrial-policy-psu-msme).

Other indices (Class 11, Index Numbers)

• Agricultural production index: a ready reckoner of farm-sector performance. Related indices cover the area, production and yield of principal crops.
• Index of foreign trade: unit-value (price) and quantity indices of exports and imports. They are used to compute terms of trade.
• Sensex: BSE Sensitive Index, base 1978-79 = 100, 30 stocks from 13 sectors (detail in financial-markets-instruments).
• HDI: a composite development index (detail in development-and-hdi).
• Where to find these: the Economic Survey publishes WPI, CPI, the index of yield of principal crops, IIP and the index of foreign trade.

6. The GDP deflator vs the CPI; deflating aggregates

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GDP deflator

• GDP deflator = nominal GDP ÷ real GDP (× 100 in percentage form).
• Nominal GDP values output at current prices. Real GDP values it at base-year (constant) prices.

• Output is the same in both, so the ratio reflects only price change.

• Bread example (Class 12, National Income Accounting):

• In 2000, 100 breads × ₹10 = ₹1,000.
• In 2001, 110 breads × ₹15 = ₹1,650 nominal; at 2000 prices, 110 × ₹10 = ₹1,100 real.

• Deflator = 1,650/1,100 = 1.50, or 150. Bread prices rose 1.5 times.

• It is an implicit index: there is no separate basket. It is economy-wide, and its weights are current production, so it behaves like a Paasche index.

• GNP deflator = nominal GNP ÷ real GNP. Exercise: nominal ₹2,500 crore, real ₹3,000 crore, so the deflator = 83.3. Prices have fallen since the base year.

NCERT's three differences (Class 12, National Income Accounting)

Point	GDP deflator	CPI
Coverage	All domestically produced goods and services (consumer, capital, government)	Only the consumer basket
Imports	Excluded (not domestic output)	Included (consumers buy imported goods)
Weights	Change with each year's production	Fixed (base basket)

• Implication: a rise in crude oil prices hits the CPI directly but affects the deflator only through domestic output. A rise in machinery prices moves the deflator but hardly moves the CPI.

Deflating aggregates

• Deflating aggregates means using price indices to strip price change out of nominal totals such as national income and capital formation. Class 11, Index Numbers notes that the WPI is used for this. In practice, CPI and WPI components deflate the relevant sectors.
• Measurement debate:
• The WPI has no services, and services are now more than half of GDP.
• When WPI inflation is very low or negative (for example, 2015–16), deflating nominal output by it can overstate real GDP growth.
• Critics of the 2011-12 series point to single deflation, where output is deflated by one index. Double deflation deflates output and inputs separately. When input prices fall faster than output prices, single deflation inflates real value added.
• Fix: build a PPI, better service deflators and double deflation, alongside the 2022-23 GDP base revision (verify current).

7. Measuring inflation: rate, base effect and the vocabulary of price change

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Definition and rate

• Inflation is a general and continuing rise in the price level. It lowers the purchasing power of money.
• If inflation becomes large enough, money can lose its roles as medium of exchange and unit of account (Class 11, Index Numbers).

• It can come from excess demand (for example, deficit-financed spending when output cannot expand) or from rising costs.

• Inflation rate (year-on-year, monthly index) = (Iₜ − Iₜ₋₁₂)/Iₜ₋₁₂ × 100. India computes it monthly from the CPI and WPI.

• (NCERT outdated: gives a weekly WPI formula, (Xₜ − Xₜ₋₁)/Xₜ₋₁ × 100.)

Base effect

• Base effect: the level of the index a year ago shapes this year's year-on-year rate.
• A low base (prices were unusually low last year) inflates the current rate.

• A high base (last year saw a spike) depresses it, even if prices are still rising now.

• The RBI splits the monthly change in year-on-year inflation into momentum, the month-on-month change now, and the base effect, last year's month-on-month change dropping out.

Food inflation

• Food inflation is the rise in food prices. Food carries about 46% of CPI-C (2012 series), so food drives headline inflation.
• It is sensitive to the monsoon, heatwaves and unseasonal rain.
• Vegetables, especially TOP (tomato, onion, potato), swing sharply because they are perishable and have thin storage.

Types by pace

• Creeping inflation: slow, steady rises, below about 3% a year. Generally benign.
• Galloping inflation: double- or triple-digit annual rates. It erodes confidence in money.
• Hyperinflation: runaway inflation, conventionally over 50% a month. Examples: Germany (Weimar) 1923, Zimbabwe 2008, Venezuela (late 2010s). The currency is destroyed.

Vocabulary of direction

Term	Meaning
Disinflation	Inflation slows. Prices still rise, but more slowly (6% → 4%).
Deflation	The general price level falls. This raises the real burden of debt and makes people postpone spending.
Reflation	Deliberate policy to push inflation and output back to normal after deflation or very low inflation.

• Skewflation: prices of a narrow group (pulses, onions, food) rise sharply while overall inflation stays moderate.
• Protein inflation: prices of protein-rich foods (pulses, milk, eggs, meat, fish) rise because rising incomes shift diets faster than supply grows.
• Shrinkflation: a smaller pack at the same price, which is a hidden price rise. Index compilers must adjust for quantity to capture it.

8. Causes of inflation: demand-pull, cost-push, structural and expectations

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Demand side

• Demand-pull inflation: aggregate demand outruns available supply, or "too much money chasing too few goods".
• Class 12, Determination of Income and Employment:
• Equilibrium output may exceed full-employment output. That is excess demand (the inflationary gap), and it leads to rising prices in the long run.

• The reverse, deficient demand, leads to falling prices.

• Typical route: deficit-financed government spending when output cannot expand. More demand meets fixed supply, so prices rise.

• Output gap = actual output − potential output.
• Positive gap: the economy is running above capacity, creating inflationary pressure.
• Negative gap: slack, so pressure on prices is low.

• The RBI uses the output gap as its working measure of demand pressure (potential output in growth-theories-business-cycles).

• Money supply and prices (Class 11, Correlation, Example 2):

Price index	120	150	190	220	230
Money supply (₹ crore)	1,800	2,000	2,500	2,700	3,000

• Using step deviation, U = (X−100)/10 and V = (Y−1700)/100, gives r = 0.98. NCERT calls this "an important premise of monetary policy".
• Caution: correlation measures co-movement, not causation. Causality could run from prices to money, or a third factor could drive both (quantity theory in money-evolution-functions).

Supply side

• Cost-push inflation: rising costs of wages, raw materials or energy shift aggregate supply left, so prices rise and output falls.
• Supply shock: a sudden change in the supply of a key input. Examples: monsoon failure, heatwaves, the 1973 oil embargo, the 2022 Russia–Ukraine war (oil, gas, fertiliser, edible oil, wheat).
• Imported inflation: inflation that arrives from abroad through:
• crude oil (India imports over 85% of its needs);
• edible oils;

• rupee depreciation, which makes every import dearer.

• Wage-price spiral:

• Prices rise, so workers demand higher wages.

• Firms' costs rise, so prices rise again, and the cycle repeats.

• Greedflation: firms raise prices beyond their cost increases to widen margins, mostly in concentrated markets.

• Structural inflation: supply bottlenecks typical of developing economies, such as low farm productivity, poor storage and cold chains, infrastructure gaps and market rigidities (APMC limits, middlemen). This is the Indian structuralist reading of persistent food inflation: monetary tightening cannot grow more pulses.

Expectations

• Inflation expectations: what households, firms and markets believe future inflation will be. The RBI tracks them in its Inflation Expectations Survey of Households.
• People expect high inflation, so workers bargain for higher wages and firms raise prices early.

• Expected inflation then turns into actual inflation, a self-fulfilling loop.

• Anchoring of inflation expectations: credible monetary policy keeps expectations stable around the target, so that one-off shocks do not become persistent. India's target is 4% CPI-C ± 2% (verify current). This is why the RBI reacts early to shocks that threaten to persist, but may "look through" short vegetable spikes (framework in banking-monetary-policy).

9. Inflation and unemployment: the Phillips curve, NAIRU and stagflation

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Short run vs long run

• Phillips curve: A.W. Phillips (1958) studied UK data and found that wage inflation was high when unemployment was low. This is a short-run inverse relationship: lower unemployment comes with higher inflation.
• Policy reading in the 1960s: governments thought they could "buy" lower unemployment with a bit more inflation.
• Friedman–Phelps expectations critique (late 1960s):
• Workers eventually expect the higher inflation and demand matching wage rises.
• Real wages return to normal, and so does unemployment. Only inflation stays higher.

• The trade-off therefore vanishes once expectations adjust.

• Long-run Phillips curve: vertical at the natural rate of unemployment. There is no lasting trade-off.

• NAIRU (non-accelerating inflation rate of unemployment): the lowest unemployment rate that can be sustained without inflation accelerating. Pushing unemployment below it makes inflation rise year after year.

Stagflation

• Stagflation: high inflation, high unemployment and stagnant growth all at once.
• It followed the 1970s oil shocks. A leftward supply shift raised prices and cut output together, which the simple Phillips curve could not explain.

• It remains a risk after big supply shocks, such as 2022.

• Misery index = inflation rate + unemployment rate. It is a rough gauge of economic hardship.

Application to India

• The Phillips curve is flat or weak in India (RBI working papers; verify current), because:
• most workers are informal, and wages and unemployment are poorly measured;

• a large share of inflation is supply-driven food inflation, unrelated to labour-market slack.

• So the RBI relies on the output gap, not unemployment data, as its gauge of demand pressure. The output gap is estimated from GDP, capacity use and surveys.

10. Effects and uses: real wages, real interest rates, indexation and the inflation target

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Uses of indices (Class 11, Index Numbers)

• CPI: wage negotiation, income policy, price policy, rent control, taxation, general economic policy.
• WPI: deflating national income and capital formation; measuring general inflation.
• IIP: a quantitative picture of industrial output.

Purchasing power and real wage

• Purchasing power of money = 1/cost-of-living index.

• With CPI (1982 = 100) at 526 in January 2005, ₹1 = 100/526 = ₹0.19. A 2005 rupee was worth 19 paise of 1982.

• Real wage = (money wage/CPI) × 100. It shows what a wage buys at base-year prices.

• A money wage of ₹10,000 × 100/526 = ₹1,901 in 1982 terms.
• A worker who earned ₹3,000 in 1982 is worse off at ₹10,000 in 2005.

• To keep the 1982 living standard, the salary must be ₹3,000 × 526/100 = ₹15,780.

• Exercise (Class 11, Index Numbers, Q17): base salary ₹4,000, CPI 400. The required salary is ₹16,000. If the current salary is ₹6,000, it must rise by ₹10,000.

Indexation

• Wage indexation: raising wages in line with the CPI. An index of 150 needs a 50% raise to keep the base-year living standard.
• Dearness Allowance (DA): a cost-of-living payment to central government employees and pensioners (as Dearness Relief). It is revised twice a year (January and July) using CPI-IW.
• Indexation more broadly means adjusting incomes, liabilities or asset costs for inflation:
• Pensions (Dearness Relief).
• Tax brackets, to prevent "bracket creep".
• Capital gains: the Cost Inflation Index (CII) raises an asset's purchase cost so that only real gains are taxed. The rules changed in Budget July 2024, when indexation was largely removed for LTCG (verify current).
• Inflation-indexed bonds: principal or coupon linked to an index.

Redistribution

• Losers: creditors, fixed-income earners (pensioners without indexation, salaried workers without DA) and cash holders.
• Gainers: debtors, who repay loans in cheaper rupees. The government is a big debtor.
• The poor lose most. Food is a large share of their spending and they have few inflation-proof assets.
• Inflation tax: the hidden loss of purchasing power borne by holders of money and fixed-income assets when government spending is financed by printing money.

Real interest rate

• Real interest rate = nominal interest rate − (expected) inflation. This is the Fisher relation.
• Example: an 7% FD with 6% inflation gives a real return of about 1%.
• Negative real rates (inflation above the deposit rate) erode savers' returns. Households then shift from bank deposits to gold, real estate or equities.

CPI-C as the policy anchor

• Flexible inflation targeting: recommended by the Urjit Patel Committee (2014), given legal backing by the RBI Act amendment (2016). The target is 4% CPI-C, band 2–6%, reviewed every five years (current period: verify current). MPC detail in banking-monetary-policy.
• The government's supply-side tools against food inflation (detail in agri-marketing-msp-pds):
• release of buffer stocks, for example open-market sales of wheat and rice;
• stock limits on traders;
• export curbs or bans (wheat, rice, onion);
• import-duty cuts (edible oils, pulses).
• Cost: these tools lower consumer prices but can depress farmers' incomes.

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Exam angles

Prelims — high-yield facts and traps

• Agency matches:
• CPI-IW, CPI-AL and CPI-RL → Labour Bureau.
• CPI Rural/Urban/Combined, CFPI and IIP → NSO (MoSPI).

• WPI and the eight-core index → OEA, DPIIT.

• Use matches:

• CPI-IW → DA of government employees and industrial wages.
• CPI-AL/RL → agricultural and rural minimum wages.

• CPI-C → RBI's inflation target.

• Base years: CPI-IW 2016 (since 2020); CPI-C 2012 → 2024; WPI/IIP/GDP 2011-12 → 2022-23 (verify current); CPI-AL/RL 1986-87 → newer (verify current).

• Statement traps:
• "WPI includes services." FALSE.
• "The GDP deflator includes imported goods." FALSE. The CPI includes them; the deflator does not.
• "The GDP deflator has fixed weights." FALSE. Its weights change with production; CPI weights are fixed.
• "India's headline inflation is WPI-based." FALSE today. It is CPI-C.
• "CFPI excludes alcoholic beverages." FALSE. CFPI excludes non-alcoholic beverages and prepared meals; alcohol is not in the food group at all.
• "The IIP is a price index." FALSE. It is a quantity index using Laspeyres value-added weights.
• In the IIP, manufacturing has the largest sectoral weight (77.6).
• "The eight core industries weigh about 60% of the IIP." FALSE. The figure is 40.27%.

• "CPI-UNME is still compiled." FALSE. It was replaced by CPI-Urban.

• Formulas:

• Laspeyres = Σp₁q₀/Σp₀q₀ × 100 (base quantities). Paasche = Σp₁q₁/Σp₀q₁ × 100 (current quantities).
• Price relative = p₁/p₀ × 100.
• Real wage = money wage/CPI × 100. Purchasing power = 1/CPI.
• Real interest rate = nominal − inflation.

• GDP deflator = nominal/real GDP × 100.

• Bias: Laspeyres overstates and Paasche understates the rise in the cost of living.

• Weights:
• CPI-C food about 46 (2012 series), lower in the 2024 series (verify current); CFPI about 39.
• WPI: manufactured 64.23, primary 22.62, fuel 13.15; WPI Food Index 24.23.

• IIP: primary goods 34.1 is the largest use-based group; capital goods 8.2 the smallest.

• Vocabulary pairs:

• Disinflation (slower rise) vs deflation (fall) vs reflation (deliberate push back up).
• Skewflation (narrow group); stagflation (inflation + unemployment + stagnation).
• Base effect; long-run Phillips curve vertical at the natural rate; NAIRU; misery index = inflation + unemployment.
• Hyperinflation: more than 50% a month.

Mains — GS-III themes

1. Which index should anchor monetary policy? - Why CPI over WPI: it measures consumers' cost of living, includes services and shapes expectations. - Should the RBI target headline or core, given food's heavy weight? - Implications of the new CPI base: a lower food share may make headline inflation less volatile.

2. Food inflation: structural or supply shock? - Drivers: monsoon and heatwaves, pulses and protein inflation, TOP volatility. - Limits of monetary policy against supply shocks. - Supply-side responses (buffer stocks, stock limits, export bans, duty cuts) and their costs to farmers.

3. Distributional effects of inflation: - The poor spend more of their budget on food; fixed-income earners and savers lose from negative real rates; the inflation tax. - The case for indexation: DA, pensions, inflation-indexed bonds, CII.

4. Measurement quality: - Base-year revision and alignment across indices. - The WPI-to-PPI shift; single vs double deflation and the accuracy of real GDP. - What WPI–CPI divergence signals.

5. Diagnosis of an inflation episode: - Demand-pull vs cost-push, for example post-COVID and the 2022 commodity shock. - Output gap, imported inflation via crude and the rupee, and anchoring expectations. - Why the Phillips curve fits India weakly.

Current-affairs hooks

• Monthly data releases:
• CPI (around the 12th, NSO).
• WPI (around the 14th, OEA-DPIIT).
• IIP (NSO) and the Index of Eight Core Industries (DPIIT).

• The new CPI 2024-base series and the WPI/IIP/GDP 2022-23 base revisions (verify current).

• RBI:

• Bi-monthly MPC statements and the half-yearly Monetary Policy Report (inflation projections).
• The Inflation Expectations Survey of Households.

• Review of the 4% ± 2% target for the next five-year period (verify current).

• Government policy:

• Economic Survey chapter on prices and inflation.
• Budget changes to fuel and food taxes and import duties.

• Export bans and stock limits on wheat, rice, onion and pulses.

• Wages and global shocks:

• DA/DR hikes linked to CPI-IW; Pay Commission announcements.
• Global inflation and oil shocks from OPEC+ decisions and geopolitical supply disruptions.