EconomicsCBSE Class 12 · National Income Accounting

Real and Nominal GDP, GDP Deflator and GDP as an Index of Welfare (Class 12)

Updated 15 October 2026 · Fact-checked

Nominal GDP values a year's output at that year's prices; real GDP values it at constant base-year prices, so it changes only when output changes. GDP deflator = nominal GDP ÷ real GDP × 100 and measures the change in prices. GDP is not a perfect index of welfare because it ignores distribution, non-monetary exchanges and externalities.

Deflator = nominal ÷ real × 100 shows price change, while GDP still ignores who gains, unpaid work and pollution.

Illustration drawn for QuestionBuddy.

Understand Real and Nominal GDP, GDP Deflator and Welfare

Nominal vs real.

Nominal GDP (GDP at current prices): Σ (current year quantity × current year price). It can rise because output rises, because prices rise, or both.
Real GDP (GDP at constant prices): Σ (current year quantity × base year price). Prices are held fixed, so it changes only when physical output changes. Real GDP is therefore the better measure of economic growth.
In the base year, nominal GDP = real GDP.

GDP deflator. Deflator = Nominal GDP ÷ Real GDP × 100. A deflator of 120 means prices are on average 20% higher than in the base year. Real GDP = Nominal GDP ÷ Deflator × 100. Unlike the consumer price index, the deflator covers all goods and services produced in the economy (including capital goods), not a fixed basket bought by consumers.

Real growth. Real growth rate = (Real GDP this year − Real GDP last year) ÷ Real GDP last year × 100. Approximately, real growth ≈ nominal growth − inflation.

GDP and welfare. Higher GDP often means more goods and services, but it is not a perfect index of welfare:
1. Distribution of GDP: GDP may rise while the income of most people falls, if gains go to a few.
2. Non-monetary exchanges: services of homemakers, barter and own-account work in the informal sector are not counted, so GDP understates true activity.
3. Externalities: benefits or harms to others not paid for are ignored. A factory's output adds to GDP, but the pollution it causes to a river reduces welfare without being deducted (negative externality); a beautiful garden benefiting neighbours is a positive externality not counted.
Also, the composition of GDP matters: more spending on defence or on goods harmful to health may not raise welfare.

Real and Nominal GDP, GDP Deflator and Welfare: key facts

Nominal GDP: Σ (current quantity × current price)
Real GDP: Σ (current quantity × base-year price)
GDP deflator: Nominal GDP ÷ Real GDP × 100
Real GDP from deflator: Nominal GDP ÷ Deflator × 100
Real growth rate: (Real GDP₂ − Real GDP₁) ÷ Real GDP₁ × 100; ≈ nominal growth − inflation.

How to answer Real and Nominal GDP, GDP Deflator and Welfare questions

Real-nominal questions are short numericals; welfare questions are 3- or 4-mark reasoning items.

1Compute nominal GDP with current prices and real GDP with base-year prices.
2Deflator = nominal ÷ real × 100; read it as a price level relative to the base year.
3For real growth, compare real GDP of the two years, not nominal.
4For welfare, use the three limitations: distribution, non-monetary exchanges, externalities.
5Give a short example for each limitation.
6State the conclusion: GDP is a useful but incomplete index of welfare.

Real and Nominal GDP, GDP Deflator and Welfare in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Nominal vs real

Suppose your monthly pocket money rises from ₹500 to ₹1,000 over some years, and over the same period the prices of everything you buy also double.

Has your 'real' pocket money changed? Relate this to nominal and real GDP.

Try it first, then show the solutionSolution

Nominal pocket money doubled: ₹500 → ₹1,000.
Prices doubled: a price index of 100 → 200.
Real pocket money = 1,000 ÷ 200 × 100 = ₹500: unchanged.

Answer: No. In real terms you can buy exactly what you could before. Likewise, nominal GDP can rise purely because of inflation; real GDP removes the price effect and shows whether output actually grew.

Memory hook: Twice the rupees at twice the prices buys the same basket.

Tricks to remember Real and Nominal GDP, GDP Deflator and Welfare

Short memory aids. Say each one aloud once, then use it on a question the same day.

Nominal = Now prices, Real = base pRices
N for Now, R for Reference (base) year.
Use it when: Definitions.
Deflator = N ÷ R × 100
Nominal on top, Real below.
Use it when: Deflator formula.
D-N-E
Distribution, Non-monetary exchanges, Externalities: why GDP ≠ welfare.
Use it when: Welfare limitations.

Real and Nominal GDP, GDP Deflator and Welfare: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: GDP deflator · 1 mark · MCQBoard level

Nominal GDP is ₹2,400 crore and real GDP is ₹2,000 crore. The GDP deflator is:
(a) 83.33
(b) 120
(c) 20
(d) 400

Try it first, then show the solutionSolution

Deflator = 2,400 ÷ 2,000 × 100 = 120.

Answer: (b) 120

Example 2: Two-good economy · 3 marks · Short answerBoard level

An economy produces rice and cloth. Base year: rice 10 units at ₹20, cloth 5 units at ₹100. Current year: rice 12 units at ₹25, cloth 6 units at ₹110. Calculate nominal GDP, real GDP and the GDP deflator for the current year. (3 marks)

Try it first, then show the solutionSolution

Nominal = 12 × 25 + 6 × 110 = 300 + 660 = ₹960.
Real (base prices) = 12 × 20 + 6 × 100 = 240 + 600 = ₹840.
Deflator = 960 ÷ 840 × 100 = 114.29.

Answer: Nominal ₹960; real ₹840; deflator 114.29.

Example 3: Nominal vs real growth · 3 marks · Short answerHarder board level

Nominal GDP rose from ₹1,000 crore (base year, deflator 100) to ₹1,320 crore, and the deflator rose to 110. Calculate real GDP in the second year and the real growth rate. Compare with nominal growth. (3 marks)

Try it first, then show the solutionSolution

Real GDP = 1,320 ÷ 110 × 100 = ₹1,200 crore.
Real growth = (1,200 − 1,000) ÷ 1,000 × 100 = 20%.
Nominal growth = 32%; the extra 12 percentage points came from higher prices.

Answer: Real GDP ₹1,200 crore; real growth 20% against nominal growth 32%.

Example 4: GDP and welfare · 4 marks · Short answerHarder board level

'An increase in GDP may not lead to an increase in welfare.' Explain with three reasons. (4 marks)

Try it first, then show the solutionSolution

Distribution: if the rise goes mainly to a few rich people, most people may be no better off.
Non-monetary exchanges: unpaid household services and barter are not counted, so GDP misstates activity.
Externalities: pollution from factories reduces welfare but is not deducted from GDP.
Composition: more output of defence goods or harmful products may not improve welfare.

Answer: GDP is an incomplete index of welfare because of its distribution, non-monetary exchanges and externalities (and composition).

Example 5: Working back to nominal GDP · 3 marks · Short answerHOTS / competency

Real GDP is ₹5,000 crore and the GDP deflator is 125. Calculate nominal GDP and state what the deflator tells you. (3 marks)

Try it first, then show the solutionSolution

Nominal = Real × Deflator ÷ 100 = 5,000 × 125 ÷ 100 = ₹6,250 crore.
Deflator 125: the general price level of domestic output is 25% above the base year.

Answer: Nominal GDP ₹6,250 crore; prices are 25% higher than in the base year.

Example 6: Rising nominal GDP · 1 mark · Assertion-reasonHOTS / competency

Assertion (A): A rise in nominal GDP always means that more goods and services have been produced.
Reason (R): Nominal GDP can rise because of a rise in prices even when output is unchanged.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Try it first, then show the solutionSolution

R shows a counterexample to A; A is false.

Answer: (d) A is false, but R is true.

Where students lose marks in Real and Nominal GDP, GDP Deflator and Welfare

The slips examiners see most often, and what to write instead.

Mistake: Using current prices for real GDP
Mixing the two definitions.
Wrong working
Real GDP = Σ current quantity × current price.
Right working
Real GDP = Σ current quantity × base-year price.
Do this: Real = base prices.
Usually costs: 1 mark.
Mistake: Inverting the deflator
Dividing real by nominal.
Wrong working
Deflator = 840 ÷ 960 × 100 = 87.5.
Right working
Deflator = 960 ÷ 840 × 100 = 114.29.
Do this: Nominal on top.
Usually costs: 1 mark.
Mistake: Measuring growth with nominal GDP
Using the figures given.
Wrong working
Growth = 32%.
Right working
Real growth = 20%.
Do this: Growth means real output.
Usually costs: 1 mark.
Mistake: Explaining externalities without an example
Abstract answers.
Wrong working
'Externalities are not included.'
Right working
'Pollution from a factory harms people downstream; its cost is not deducted from GDP.'
Do this: Always give an example.
Usually costs: 1/2 to 1 mark.

Exam tips

Show the price used (base or current) in each multiplication.
Round the deflator to two decimals.
For welfare answers, use the three textbook headings with one example each.
Real vs nominal GDP and GDP-welfare appear as 3- and 4-mark questions regularly.

Practice questions on Real and Nominal GDP, GDP Deflator and Welfare

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Real GDP is GDP measured at:
(a) current year prices
(b) base year prices
(c) factor cost
(d) market price including indirect taxes
Hint
Constant prices.
Answer
(b) base year prices
Q2 · 1 mark · MCQBoard level
GDP deflator is calculated as:
(a) Real GDP ÷ Nominal GDP × 100
(b) Nominal GDP ÷ Real GDP × 100
(c) Nominal GDP − Real GDP
(d) Real GDP × Nominal GDP
Hint
Nominal on top.
Answer
(b) Nominal GDP ÷ Real GDP × 100
Q3 · 3 marks · Short answerBoard level
Nominal GDP is ₹3,300 crore and the deflator is 110. Calculate real GDP and interpret the deflator. (3 marks)
Hint
Divide by 1.1.
Answer
Real GDP = 3,300 ÷ 110 × 100 = ₹3,000 crore. Deflator 110 means prices are 10% higher than in the base year.
Q4 · 4 marks · Short answerHarder board level
Base year: apples 100 units at ₹10, bananas 200 units at ₹5. Current year: apples 120 units at ₹12, bananas 220 units at ₹6. Calculate nominal GDP, real GDP and the deflator for the current year. (4 marks)
Hint
Real uses ₹10 and ₹5.
Answer
Nominal = 1,440 + 1,320 = ₹2,760; real = 1,200 + 1,100 = ₹2,300; deflator = 120.
Q5 · 3 marks · Short answerHarder board level
Explain, with an example, how externalities make GDP a poor index of welfare. (3 marks)
Hint
Harm not deducted.
Answer
Externalities are benefits or harms to others for which no payment is made. A chemical factory's output adds to GDP, but its waste pollutes a river and harms farmers and fishermen; this loss of welfare is not deducted, so GDP overstates welfare. Positive externalities, like a public park's benefits, are likewise not counted.
Q6 · 3 marks · Short answerHarder board level
Nominal GDP rose from ₹2,000 crore to ₹2,420 crore and the deflator from 100 to 110. Calculate the real growth rate. (3 marks)
Hint
Real GDP year 2 first.
Answer
Real GDP year 2 = 2,420 ÷ 1.1 = ₹2,200 crore; real growth = 10%.
Q7 · 3 marks · Short answerHarder board level
Why is real GDP a better measure of economic growth than nominal GDP? (3 marks)
Hint
Price effect.
Answer
Nominal GDP changes with both output and prices, so it can rise only because of inflation. Real GDP values output at constant base-year prices, so it changes only when the quantity of goods and services changes, making it the true measure of growth.
Q8 · 1 mark · Assertion-reasonHarder board level
Assertion (A): GDP is a perfect index of the welfare of people.
Reason (R): GDP ignores non-monetary exchanges and externalities.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Hint
What R implies about A.
Answer
(d) A is false, but R is true.
Q9 · 3 marks · Short answerHOTS / competency
Country X's nominal GDP grew 12% with 10% inflation; Country Y's grew 8% with 2% inflation. Which had faster real growth? Show approximate calculations. (3 marks)
Hint
Real ≈ (1 + nominal) ÷ (1 + inflation) − 1.
Answer
X: 1.12 ÷ 1.10 − 1 ≈ 1.8%; Y: 1.08 ÷ 1.02 − 1 ≈ 5.9%. Y grew faster in real terms despite lower nominal growth.
Q10 · 3 marks · Short answerHOTS / competency
Suppose the government's output rises because it spends more on building weapons, while spending on schools stays the same. GDP rises. Does welfare necessarily rise? Explain. (3 marks)
Hint
Composition of GDP.
Answer
Not necessarily. GDP counts all final output equally, but welfare depends on what is produced and who benefits. More weapons may add to security but do not raise living standards like education or health would, so the composition of GDP matters for welfare.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Define nominal GDP.Show answer
GDP valued at current year prices.
2.Deflator if nominal = real?Show answer
100 (the base year).
3.Real GDP when nominal is ₹4,400 crore and deflator 110?Show answer
₹4,000 crore.
4.Name three reasons GDP is not a perfect index of welfare.Show answer
Distribution of GDP, non-monetary exchanges, externalities.
5.Which is the better measure of growth?Show answer
Real GDP.

Real and Nominal GDP, GDP Deflator and Welfare: frequently asked questions

What is the difference between real and nominal GDP in Class 12?

Nominal GDP uses current prices; real GDP uses constant base-year prices, so it reflects only changes in output.

What does the GDP deflator measure?

The average change in prices of all goods and services produced, relative to the base year.

Why is GDP not a good index of welfare?

It ignores how income is distributed, excludes non-monetary exchanges, and does not account for externalities such as pollution.

How is the deflator different from CPI?

The deflator covers all domestically produced goods and services, including capital goods; CPI covers a fixed basket of goods bought by consumers, including imports.