अर्थशास्त्र Economics

Quick summary

Economics is the study of how people, firms and governments use scarce resources to satisfy unlimited wants. This topic covers the main definitions of economics (Adam Smith, Marshall, Robbins, Samuelson), the basic economic problem, and the difference between micro and macro economics.

Key points

• The word economics comes from the Greek word oikonomia, meaning management of the household.
• Adam Smith (1776, The Wealth of Nations) gave the wealth definition: economics is the science of wealth. He is called the Father of Economics.
• Alfred Marshall (1890, Principles of Economics) gave the welfare definition: economics studies mankind in the ordinary business of life — how people earn and use income to get material welfare.
• Lionel Robbins (1932) gave the scarcity definition: economics studies human behaviour as a relationship between ends (wants) and scarce means which have alternative uses.
• Paul Samuelson gave the growth definition: economics studies how society chooses to use scarce resources to produce goods over time and distribute them for present and future consumption.
• The central problem of every economy is choice, because wants are unlimited and resources are limited. The three basic questions are: What to produce? How to produce? For whom to produce?
• Microeconomics studies individual units (a consumer, a firm, the price of one good). It is also called price theory.
• Macroeconomics studies the economy as a whole (national income, employment, general price level). It is also called income theory. The terms "micro" and "macro" were first used by Ragnar Frisch in 1933; macroeconomics became popular after Keynes (1936).
• Positive economics describes "what is"; normative economics says "what ought to be".
• Economics is both a science (it studies cause and effect) and an art (it helps solve practical problems).

Important terms

• Scarcity (टंचाई) – resources are limited compared to wants.
• Opportunity cost – the value of the next best alternative given up when a choice is made.
• Want – a desire for a good or service backed by the need to satisfy it.
• Economic good – a good that is scarce and has a price.
• Free good – a good available in plenty without a price, e.g. air.
• Production possibility curve (PPC) – a curve showing the different combinations of two goods an economy can produce with given resources and technology.

Key facts

• The PPC slopes downward from left to right and is concave to the origin, because of increasing opportunity cost.
• Opportunity cost along the PPC = units of good Y given up ÷ extra units of good X gained.

5 important questions

Q1. What is microeconomics?

Microeconomics studies the behaviour of individual economic units such as a consumer, a firm or an industry. It explains how the price of a single good is decided. It is also called price theory.

Q2. Define opportunity cost.

Opportunity cost is the benefit of the next best alternative that is given up when we make a choice. For example, if land is used to grow wheat, the rice that could have been grown is its opportunity cost.

Q3. Explain Robbins' scarcity definition of economics and its criticism.

• Definition: economics studies human behaviour as a relationship between ends and scarce means having alternative uses.
• Features: unlimited ends (wants); scarce means; alternative uses of means; need for choice.
• Merits: universal, scientific, applies to all economies.
• Criticism: ignores human welfare; treats economics as neutral between ends; does not explain growth of resources; ignores macro problems like unemployment (Keynes).

Q4. Distinguish between microeconomics and macroeconomics.

• Unit of study: individual units vs economy as a whole.
• Main tool: price mechanism (demand and supply) vs aggregate demand and aggregate supply.
• Other name: price theory vs income and employment theory.
• Examples: price of rice, a firm's output vs national income, inflation, unemployment.
• Both are interdependent; one cannot be fully understood without the other.

Q5. What is the central problem of an economy? Explain with the help of the PPC.

• Wants unlimited, resources scarce, so choice is needed.
• Three questions: what, how and for whom to produce.
• PPC shows combinations of two goods with full use of resources.
• A point on the curve = efficient use; inside the curve = unemployment of resources; outside = not possible now.
• Shift of PPC to the right = economic growth.

Exam tip

Learn the four definitions with the name, year and one-word label (wealth, welfare, scarcity, growth). Draw and label the PPC whenever you write about the central problem.

Quick summary

Every society must solve the same basic problems: what to produce, how to produce, for whom to produce, and how to grow. An economic system is the set of institutions through which a society answers these questions. The three main types are capitalism (market economy), socialism (command economy) and the mixed economy, which India follows.

Key points

• Central problems arise because resources are scarce and have alternative uses, while wants are unlimited.
• Capitalism (free-market economy): means of production are privately owned; decisions are guided by the price mechanism and the profit motive. Examples: USA, UK (largely).
• Features of capitalism: right to private property, freedom of enterprise, consumer sovereignty, competition, profit motive, inheritance, minimal state role (laissez-faire).
• Merits: efficiency, innovation, wide consumer choice, automatic working through prices. Demerits: inequality of income, monopolies, trade cycles and unemployment, neglect of public goods.
• Socialism (command economy): means of production owned and controlled by the state; decisions taken by a central planning authority. Examples: former USSR, Cuba.
• Features of socialism: social ownership, central planning, equality, absence of profit motive in key sectors, limited consumer choice.
• Merits: equality, full use of resources, no exploitation, social welfare. Demerits: bureaucracy, lack of incentive, inefficiency, loss of freedom, black markets.
• Mixed economy: public and private sectors exist side by side; prices work but the state regulates and plans. India chose this after 1950 (Industrial Policy 1948 and 1956).
• After 1991 India moved towards a more market-oriented mixed economy (LPG reforms).

Important terms

• Price mechanism – the free working of demand and supply that decides prices and resource allocation.
• Consumer sovereignty (उपभोक्ता सार्वभौमत्व) – consumers' choices decide what is produced.
• Laissez-faire – policy of non-interference by the state in economic matters.
• Central planning authority – a state body that takes all major economic decisions in a command economy.
• Public sector – enterprises owned and managed by the government.
• Private sector – enterprises owned by individuals or companies for profit.

Key facts

5 important questions

Q1. What are the central problems of an economy?

What to produce and in what quantity, how to produce (which technique), for whom to produce (distribution), and how to ensure full use and growth of resources.

Q2. Define consumer sovereignty.

It means the consumer is "king": what goods are produced and in what quantity is decided by consumers' demand in the market.

Q3. Explain the features, merits and demerits of capitalism.

Outline: meaning; features (private property, freedom of enterprise, price mechanism, competition, profit motive, consumer sovereignty, laissez-faire); merits (efficiency, growth, innovation, choice); demerits (inequality, monopoly, cyclical unemployment, waste in advertising, neglect of the poor); conclusion – pure capitalism rarely exists today.

Q4. What is socialism? Discuss its merits and limitations.

Outline: meaning and examples; features (state ownership, central planning, equality, no exploitation); merits (equality, planned growth, social security, full employment); limitations (bureaucracy, lack of incentives, inefficiency, loss of freedom, wrong pricing); collapse of the USSR in 1991.

Q5. Explain the mixed economy with special reference to India.

Outline: meaning; features (co-existence of public and private sectors, planning, regulation, welfare goals, price mechanism); India's case – Industrial Policy 1948 and 1956, Five-Year Plans, public sector in heavy industry; changes after 1991 (liberalisation, privatisation); merits and problems (inefficient PSUs, red tape); conclusion.

Exam tip

Draw the three-column comparison table in long answers – it earns marks quickly and shows clear understanding.

Quick summary

Demand means the quantity of a good that consumers are willing and able to buy at a given price during a given time. This topic covers the determinants of demand, the law of demand, its exceptions, and the difference between movement along and shift of the demand curve.

Key points

• Demand needs three things: desire, ability to pay (purchasing power) and willingness to pay. Demand is always stated with a price and a time period.
• Demand function: Dx = f(Px, Py, Y, T, E...) – demand for good x depends on its own price, prices of related goods, income, tastes and expectations.
• Law of demand (stated by Marshall): other things remaining the same, when the price of a good falls, its quantity demanded rises, and when the price rises, quantity demanded falls. Price and demand are inversely related.
• Assumptions (ceteris paribus): income, tastes, prices of related goods, population and expectations remain constant.
• The demand curve slopes downward from left to right.
• Reasons for downward slope: law of diminishing marginal utility, income effect, substitution effect, new buyers entering at lower price, multiple uses of a good.
• Exceptions: Giffen goods (inferior goods like coarse grain for the very poor), Veblen or prestige goods (diamonds), expectation of future price change, ignorance of quality, emergencies such as war or famine.
• Movement along the curve (extension or contraction of demand) happens only due to a change in the good's own price.
• Shift of the curve (increase or decrease in demand) happens due to change in other factors like income or tastes. A rightward shift means increase; a leftward shift means decrease.
• Market demand is the horizontal sum of individual demands at each price.

Important terms

• Demand schedule – a table showing quantities demanded at different prices.
• Normal good – demand rises when income rises.
• Inferior good – demand falls when income rises.
• Substitutes – goods used in place of each other, e.g. tea and coffee.
• Complements – goods used together, e.g. car and petrol.
• Giffen paradox – for a Giffen good, a fall in price reduces demand (named after Sir Robert Giffen).
• Veblen effect – status goods are demanded more at higher prices (Thorstein Veblen).

Key facts

• Law of demand: P ↑ → Qd ↓ and P ↓ → Qd ↑ (inverse relation).
• Price of substitute ↑ → demand for good ↑ (curve shifts right).
• Price of complement ↑ → demand for good ↓ (curve shifts left).
• Income ↑ → demand for normal good ↑, for inferior good ↓.

5 important questions

Q1. State the law of demand.

Other things remaining constant, the quantity demanded of a good rises when its price falls and falls when its price rises. There is an inverse relation between price and quantity demanded.

Q2. What is a Giffen good?

A Giffen good is an inferior good on which poor people spend a large part of their income, e.g. coarse grain. When its price falls, they buy less of it and more of better food. So the law of demand does not apply.

Q3. Explain the law of demand with its assumptions and exceptions.

• Statement of the law; schedule and downward-sloping curve.
• Assumptions: constant income, tastes, prices of related goods, population, no expected price change.
• Exceptions: Giffen goods, prestige goods, speculation, ignorance, emergencies, necessities.
• Conclusion: law is qualitative, not quantitative.

Q4. Why does the demand curve slope downward?

• Diminishing marginal utility: buyer buys more only at lower price.
• Income effect: lower price raises real income.
• Substitution effect: good becomes cheaper than substitutes.
• New consumers enter the market.
• Different uses: cheaper good is put to more uses (e.g. electricity).

Q5. Distinguish between change in quantity demanded and change in demand.

• Cause: own price vs other factors (income, tastes, related prices).
• Diagram: movement along same curve vs shift of whole curve.
• Names: extension/contraction vs increase/decrease.
• Example: fall in price of mangoes vs rise in income of buyers.

Exam tip

Always write "other things remaining the same" when stating the law. In diagrams, label axes clearly: price on the Y-axis, quantity on the X-axis.

Quick summary

Elasticity of demand measures how much the quantity demanded responds to a change in price, income or the price of a related good. Marshall developed the idea of price elasticity. This topic covers its types, degrees, methods of measurement and the factors that affect it.

Key points

• Price elasticity of demand (Ep) = percentage change in quantity demanded ÷ percentage change in price. The minus sign is usually ignored because price and demand move in opposite directions.
• Perfectly elastic (Ep = ∞) – horizontal demand curve.
• Relatively elastic (Ep > 1) – flatter curve; luxuries.
• Unitary elastic (Ep = 1) – rectangular hyperbola.
• Relatively inelastic (Ep < 1) – steeper curve; necessities.
• Perfectly inelastic (Ep = 0) – vertical demand curve.
• Five degrees of price elasticity:
• Income elasticity is positive for normal goods, negative for inferior goods.
• Cross elasticity is positive for substitutes and negative for complements.
• Methods of measurement: percentage (proportionate) method, total outlay (expenditure) method, point (geometric) method and arc method.
• Total outlay method (Marshall): if price falls and total expenditure rises, Ep > 1; if expenditure stays same, Ep = 1; if expenditure falls, Ep < 1.
• Factors affecting elasticity: nature of the good (necessity or luxury), availability of substitutes, number of uses, share of income spent, postponement of use, habits, time period, price level.
• Uses: pricing decisions by firms and monopolists, taxation policy by government, price discrimination, international trade, wage fixing.

Important terms

• Elasticity (लवचिकता) – degree of responsiveness of demand.
• Point elasticity – elasticity at a point on a straight-line demand curve = lower segment ÷ upper segment.
• Arc elasticity – elasticity between two points on a curve, using average price and average quantity.
• Total outlay – price × quantity bought.

Formulas

• Ep = (ΔQ/Q) ÷ (ΔP/P) = (ΔQ/ΔP) × (P/Q)
• Arc elasticity = [ΔQ / (Q₁ + Q₂)] ÷ [ΔP / (P₁ + P₂)]
• Point elasticity (straight-line curve) = lower segment ÷ upper segment
• Income elasticity Ey = (ΔQ/Q) ÷ (ΔY/Y)
• Cross elasticity Exy = (ΔQx/Qx) ÷ (ΔPy/Py)

Here Q = quantity, P = price, Y = income, Δ = change.

5 important questions

Q1. Define price elasticity of demand.

It is the ratio of the percentage change in quantity demanded to the percentage change in price. It shows how sensitive buyers are to a price change.

Q2. Price of a pen falls from Rs. 10 to Rs. 8 and demand rises from 100 to 150 pens. Find Ep.

• ΔQ = 150 − 100 = 50; ΔP = 10 − 8 = 2 (fall).
• Ep = (ΔQ/ΔP) × (P/Q) = (50/2) × (10/100) = 25 × 0.1 = 2.5.
• Ep > 1, so demand is relatively elastic.

Q3. Explain the degrees of price elasticity of demand with diagrams.

• Perfectly elastic: horizontal line parallel to X-axis.
• Perfectly inelastic: vertical line parallel to Y-axis.
• Unitary: rectangular hyperbola; total outlay constant.
• Relatively elastic: flatter curve; small price change, big demand change.
• Relatively inelastic: steeper curve; big price change, small demand change.
• Give one example of each (salt for inelastic, AC for elastic).

Q4. Explain the total outlay method with an example.

• Compare total expenditure before and after price change.
• Price falls from Rs. 5 to Rs. 4, quantity rises from 10 to 15: outlay rises from 50 to 60, so Ep > 1.
• If outlay remains 50, Ep = 1; if it falls, Ep < 1.
• Limitation: tells only whether Ep is more, equal or less than 1, not the exact value.

Q5. What factors determine the elasticity of demand?

• Necessities inelastic, luxuries elastic.
• More substitutes → more elastic.
• Goods with many uses → elastic.
• Small share of budget (salt, matchbox) → inelastic.
• Use can be postponed → elastic.
• Habit-forming goods → inelastic.
• Long run → more elastic than short run.

Exam tip

In numerical questions, write the formula first, then substitute values, then state the type of elasticity. Examiners give marks for each step.

Quick summary

Supply is the quantity of a good that sellers are willing and able to offer for sale at a given price during a given time. The law of supply says that, other things remaining the same, quantity supplied rises when price rises and falls when price falls. Elasticity of supply measures how strongly quantity supplied responds to a change in price.

Key points

• Supply differs from stock: stock is the total quantity available; supply is the part actually offered at a price.
• Determinants of supply: price of the good, cost of production (input prices), technology, prices of related goods, goals of the firm, government policy (taxes and subsidies), number of sellers, expectations, natural factors (for farm goods).
• Law of supply: price and quantity supplied move in the same direction (direct relation), ceteris paribus. The supply curve slopes upward from left to right.
• Reasons: higher price means higher profit; new firms enter; firms can cover rising marginal cost.
• Exceptions: backward-bending supply of labour, perishable goods in distress sale, expected fall in price, rare goods (paintings) whose supply is fixed, agricultural goods in the short run.
• Movement along the curve (extension/contraction) – caused only by change in own price.
• Shift of the curve (increase/decrease) – caused by change in other factors, e.g. better technology shifts supply to the right.
• Elasticity of supply (Es) = % change in quantity supplied ÷ % change in price.
• Five degrees: perfectly elastic (Es = ∞), relatively elastic (Es > 1), unitary (Es = 1), relatively inelastic (Es < 1), perfectly inelastic (Es = 0).
• Factors affecting Es: time period (supply is more elastic in the long run), nature of the good (perishable vs durable), cost behaviour, availability of spare capacity, storage facilities.

Important terms

• Supply schedule – a table showing quantities supplied at different prices.
• Extension of supply (पुरवठ्याचा विस्तार) – more supplied because price rose.
• Contraction of supply – less supplied because price fell.
• Increase in supply – more supplied at the same price (rightward shift).
• Market period – a very short time in which supply is fixed (Es = 0).

Formulas

• Es = (ΔQ/Q) ÷ (ΔP/P) = (ΔQ/ΔP) × (P/Q)
• A straight-line supply curve through the origin has Es = 1; one that cuts the price axis has Es > 1; one that cuts the quantity axis has Es < 1.

Worked example: price rises from ₹10 to ₹12, quantity supplied rises from 100 to 130 units.
ΔQ/Q = 30/100 = 0.30; ΔP/P = 2/10 = 0.20; Es = 0.30 ÷ 0.20 = 1.5 (relatively elastic).

5 important questions

Q1. State the law of supply.

Other things remaining constant, the quantity supplied of a good increases with a rise in its price and decreases with a fall in its price.

Q2. Distinguish between extension and increase in supply.

Extension is a movement along the same supply curve due to a rise in the good's own price. Increase is a rightward shift of the whole curve due to factors other than price, such as better technology.

Q3. Explain the law of supply with a schedule and diagram. State its assumptions and exceptions.

Outline: statement; schedule (e.g. ₹10–100 units, ₹12–130, ₹14–160); upward-sloping curve; assumptions (no change in cost, technology, taxes, related prices); reasons; exceptions (labour supply, perishable goods, expected price fall, rare goods).

Q4. What is elasticity of supply? Explain its types with diagrams.

Outline: definition and formula; five degrees with a diagram for each; geometric rule (where the line meets the axes); a numerical example.

Q5. Discuss the determinants of supply and the factors affecting elasticity of supply.

Outline: list and explain cost, technology, related prices, taxes/subsidies, number of firms, expectations, nature; then time period (Marshall's market period, short run, long run), nature of goods, spare capacity, storage.

Exam tip

Always write ceteris paribus (other things being equal) in the statement of the law, and label axes as Price (Y) and Quantity supplied (X).

Quick summary

In a competitive market the price of a good is set by the interaction of demand and supply. Equilibrium is reached where quantity demanded equals quantity supplied. This topic explains how the equilibrium price is found, what happens when demand or supply changes, the role of time (Marshall), and price controls such as price ceilings and floors.

Key points

• Market equilibrium: the point where the demand curve and supply curve intersect; Qd = Qs.
• At a price above equilibrium there is excess supply (surplus); sellers cut prices until the surplus disappears.
• At a price below equilibrium there is excess demand (shortage); buyers bid up the price.
• Marshall's scissors: both demand (utility) and supply (cost) decide price, like the two blades of a pair of scissors.
• Increase in demand (supply same) → price rises, quantity rises.
• Decrease in demand → price falls, quantity falls.
• Increase in supply (demand same) → price falls, quantity rises.
• Decrease in supply → price rises, quantity falls.
• Both increase equally → quantity rises, price unchanged.
• Effect of shifts:
• Time element (Marshall): in the market period demand dominates price; in the long run cost of production (supply) dominates.
• Price ceiling (maximum price): fixed below equilibrium to protect consumers (e.g. ration shop prices); causes shortage, queues, black market.
• Price floor (minimum support price): fixed above equilibrium to protect producers (e.g. MSP for wheat and paddy); causes surplus that the government must buy and store.
• Stable equilibrium: after a disturbance the market returns to equilibrium.

Important terms

• Equilibrium price (समतोल किंमत) – the price at which demand equals supply.
• Equilibrium quantity – the quantity bought and sold at that price.
• Excess demand – Qd > Qs at a given price.
• Excess supply – Qs > Qd at a given price.
• Market period – very short period when supply cannot change.

Formulas

• Equilibrium condition: Qd = Qs
• Linear example: Qd = 100 − 5P and Qs = 20 + 3P. 100 − 5P = 20 + 3P → 80 = 8P → P = ₹10; Q = 100 − 50 = 50 units (check: 20 + 30 = 50).

5 important questions

Q1. What is equilibrium price?

It is the price at which the quantity demanded of a good equals the quantity supplied, so there is no tendency for the price to change.

Q2. What is a price ceiling? Give one effect.

A legal maximum price fixed below the equilibrium price. It creates a shortage, which can lead to rationing and black markets.

Q3. Explain the determination of equilibrium price with a schedule and diagram.

Outline: meaning; demand and supply schedule (as in the table); diagram with D and S crossing at E; surplus above and shortage below; how the market moves back to E; Marshall's scissors.

Q4. Explain the effects of changes in demand and supply on equilibrium price.

Outline: four basic cases with diagrams; simultaneous changes (equal, demand > supply, supply > demand); real examples (onion prices after poor rains).

Q5. Discuss the role of the time element in price determination according to Marshall.

Outline: market period (fixed supply, demand decides price), short period (supply changes through variable factors), long period (all factors variable; price = cost of production), secular period; diagram for each; conclusion.

Exam tip

In numerical questions, always check your answer by putting P back into both equations – it shows the examiner your answer is correct.

Quick summary

Utility analysis (also called the cardinal approach) explains consumer behaviour by assuming that satisfaction can be measured in numbers called utils. It was developed mainly by Alfred Marshall. This topic covers total and marginal utility, the law of diminishing marginal utility, the law of equi-marginal utility and consumer's surplus.

Key points

• Utility (उपयोगिता) is the want-satisfying power of a good. It is subjective, relative and ethically neutral (a harmful good like a cigarette also has utility for a smoker).
• Total utility (TU) is the total satisfaction from all units consumed. Marginal utility (MU) is the addition to TU from one more unit.
• Law of diminishing marginal utility (stated by Gossen, popularised by Marshall): as a person consumes more units of a good continuously, the MU from each extra unit goes on falling.
• Relation of TU and MU: when MU is positive, TU rises; when MU is zero, TU is maximum; when MU is negative, TU falls.
• Assumptions of the law: units are standard and homogeneous, consumption is continuous (no time gap), consumer is rational, tastes and income do not change, utility is measurable.
• Exceptions/limitations: hobbies (stamps, coins), money (debated), music and poetry, misers, rare collections; the law fails if units are too small.
• Law of equi-marginal utility (Gossen's second law, law of substitution): a consumer gets maximum satisfaction when he spends his income so that the marginal utility of the last rupee spent on each good is equal.
• Consumer equilibrium for one good: MUx = Px (MU in money terms equals price).
• Consumer's surplus (Marshall): the difference between what a consumer is ready to pay and what he actually pays.
• Criticism of the cardinal approach: utility cannot be measured in numbers; MU of money is not constant; ignores income and substitution effects. Hicks and Allen replaced it with the ordinal (indifference curve) approach.

Important terms

• Util – an imaginary unit to measure utility.
• Cardinal utility – utility measured in numbers (1, 2, 3).
• Ordinal utility – utility only ranked (first, second).
• Rational consumer – one who aims at maximum satisfaction from his income.

Formulas

• MUn = TUn − TU(n−1)
• TU = ΣMU (sum of marginal utilities)
• Equi-marginal condition: MUx/Px = MUy/Py = ... = MU of money
• Consumer's surplus = potential price (what one is willing to pay) − actual price paid

5 important questions

Q1. What is marginal utility?

Marginal utility is the extra satisfaction a consumer gets from consuming one more unit of a good. MUn = TUn − TU(n−1).

Q2. A consumer is ready to pay Rs. 80 for a book but buys it for Rs. 60. Find consumer's surplus.

Consumer's surplus = willingness to pay − price paid = 80 − 60 = Rs. 20.

Q3. Explain the law of diminishing marginal utility with a schedule and diagram.

• Statement of the law.
• Schedule (as in the table above).
• Diagram: MU curve slopes downward from left to right and cuts the X-axis where MU = 0; TU curve rises, reaches a peak, then falls.
• Assumptions and exceptions.
• Importance: basis of law of demand, progressive taxation, value paradox.

Q4. Explain the law of equi-marginal utility.

• Consumer has limited income and many wants.
• He spends so that MU per rupee is equal in all uses.
• Table example with two goods and Rs. 1 units of money.
• Diagram: equal MU lines.
• Uses: consumption, production (factor combination), public finance.
• Limitations: indivisible goods, ignorance, habits.

Q5. Explain Marshall's concept of consumer's surplus and its criticism.

• Meaning: satisfaction above the price paid.
• Measurement: total utility in money minus total amount paid.
• Diagram: area below demand curve and above price line.
• Importance: tax policy, pricing, comparing living standards.
• Criticism: imaginary, hard to measure, assumes constant MU of money, ignores substitutes.

Exam tip

Draw TU and MU curves one above the other with the same X-axis; show TU at its peak exactly where MU touches zero.

Quick summary

Indifference curve analysis is the ordinal approach to consumer behaviour. It was developed by J.R. Hicks and R.G.D. Allen (1934), based on earlier work by Edgeworth and Pareto. The consumer only ranks combinations of goods; utility need not be measured. Equilibrium is found where the budget line touches the highest possible indifference curve.

Key points

• An indifference curve (IC) shows different combinations of two goods that give the consumer the same level of satisfaction. The consumer is indifferent between them.
• An indifference map is a set of ICs; a higher IC shows higher satisfaction.
• They slope downward from left to right (negative slope).
• They are convex to the origin (because of diminishing MRS).
• Two ICs never cut each other.
• A higher IC gives more satisfaction.
• An IC usually does not touch either axis.
• Properties of ICs:
• Marginal rate of substitution (MRSxy): the amount of good Y the consumer is willing to give up for one more unit of good X, keeping satisfaction the same. It diminishes along an IC.
• The budget line (price line) shows all combinations of two goods a consumer can buy with his income at given prices. Its slope = Px/Py.
• Consumer equilibrium conditions: (1) the budget line is tangent to the IC, i.e. MRSxy = Px/Py; (2) the IC is convex to the origin at that point.
• A change in income shifts the budget line parallel; a change in price of one good rotates it.
• Price effect = Income effect + Substitution effect (Hicks' decomposition).
• The IC approach explains the Giffen paradox, which the utility approach could not.

Important terms

• Indifference (उदासीनता) curve – locus of equal-satisfaction combinations.
• Ordinal utility – satisfaction ranked, not measured.
• Income consumption curve (ICC) – joins equilibrium points as income changes.
• Price consumption curve (PCC) – joins equilibrium points as the price of one good changes.
• Substitution effect – change in demand due to change in relative prices, real income held constant.

Formulas

• MRSxy = −ΔY/ΔX (number of Y given up per extra unit of X)
• Budget equation: M = Px·X + Py·Y (M = money income)
• Slope of budget line = Px/Py
• Equilibrium: MRSxy = Px/Py
• Price effect = Income effect + Substitution effect

5 important questions

Q1. What is an indifference curve?

It is a curve showing different combinations of two goods that give equal satisfaction to the consumer. So the consumer has no preference between any two points on it.

Q2. A consumer has Rs. 100. Px = Rs. 10, Py = Rs. 5. Write the budget equation and find the maximum of each good.

• Budget equation: 100 = 10X + 5Y.
• Only X: X = 100/10 = 10 units. Only Y: Y = 100/5 = 20 units.
• Slope of budget line = Px/Py = 10/5 = 2.

Q3. Explain the properties of indifference curves with diagrams.

• Negative slope: more X needs less Y to keep satisfaction same.
• Convex to origin: diminishing MRS.
• Never intersect: would give contradictory satisfaction levels (transitivity).
• Higher IC = higher satisfaction (more of both goods).
• Do not touch axes: consumer wants both goods.

Q4. Explain consumer's equilibrium with indifference curves.

• Assumptions: rational consumer, fixed income and prices, ordinal utility.
• Draw indifference map and budget line.
• Equilibrium at point of tangency: MRSxy = Px/Py.
• Points on higher IC unaffordable; points on lower IC give less satisfaction.
• Second condition: IC convex at the point.

Q5. Compare the cardinal utility and indifference curve approaches.

• Measurement: cardinal (utils) vs ordinal (ranking).
• Assumption of constant MU of money vs none needed.
• Tool: MU curve vs IC and budget line.
• Price effect split into income and substitution effects only in IC.
• IC explains Giffen paradox; it is more realistic.

Exam tip

Name Hicks and Allen in your first line. In the equilibrium diagram, mark the tangency point clearly and write MRSxy = Px/Py below it.

Quick summary

Consumers often get more satisfaction from a good than the price they actually pay. Alfred Marshall called this extra benefit consumer surplus. It is the difference between what a consumer is willing to pay and what he actually pays. The idea is built on the law of diminishing marginal utility and is useful in taxation, pricing and welfare policy.

Key points

• Definition (Marshall): "The excess of the price which a consumer would be willing to pay rather than go without the thing, over that which he actually does pay."
• A consumer buys units until marginal utility (in money) equals price. Earlier units give more utility than the price, so a surplus arises on them.
• Consumer surplus = Potential price (total utility in money) − Actual price paid (P × Q).
• On a diagram it is the area below the demand curve and above the price line.
• Assumptions: utility is measurable in money (cardinal), marginal utility of money is constant, diminishing marginal utility, independent utilities, no substitutes considered.
• Hicks' view: measured it with indifference curves (compensating variation), avoiding cardinal measurement.
• Criticisms: utility cannot be measured exactly; MU of money is not constant; hypothetical (imaginary); hard to measure for necessities whose potential price is infinite; ignores substitutes; differs between rich and poor.
• Importance: a monopolist and price discrimination; finance minister in choosing taxes (tax goods where surplus is large, causing less loss); comparing living standards; benefit from foreign trade and public projects (cost-benefit analysis); explains the paradox of value (water and diamonds).
• Consumer surplus is larger for necessities that are cheap (salt, matchbox).

Important terms

• Potential price – the maximum a consumer would pay rather than go without.
• Actual price – the market price paid.
• Consumer surplus (उपभोक्त्याचे संतोषाधिक्य) – the gain = potential price − actual price.
• Marginal utility of money – the satisfaction from the last rupee, assumed constant.

Formulas

• CS = Σ MU (in ₹) − (P × Q)

The consumer buys 4 units (MU = P). CS = 59 − 40 = ₹19.

5 important questions

Q1. Define consumer surplus.

It is the difference between the price a consumer is willing to pay for a good rather than go without it and the price he actually pays.

Q2. Name two assumptions of Marshall's concept.

Utility can be measured in money, and the marginal utility of money remains constant.

Q3. Explain Marshall's concept of consumer surplus with a schedule and diagram.

Outline: definition; assumptions; schedule (as above); diagram – downward demand (MU) curve, price line, shaded area = CS; how the consumer stops at MU = P.

Q4. State the criticisms of the doctrine of consumer surplus.

Outline: imaginary/hypothetical; cardinal measurement impossible; MU of money changes; necessities give infinite surplus; ignores substitutes and complementaries; differs with income; Hicks' indifference-curve restatement.

Q5. Explain the practical importance of consumer surplus.

Outline: pricing by monopolist and price discrimination; taxation policy; cost-benefit analysis of public projects; gains from international trade; comparing welfare between places; distinction between value-in-use and value-in-exchange.

Exam tip

Always shade the area between the demand curve and the price line and label it "Consumer Surplus" – it is the main mark-earner in the diagram.