Microeconomics is the branch of economics that studies individual decision-making — what a single consumer buys, what a single firm produces, and how a single market clears. The word "micro" (Greek for small) signals that the lens is narrow: one household, one firm, one market at a time. This is the opposite of macroeconomics, which looks at the entire economy (GDP, inflation, unemployment).
The central problem microeconomics is built on is scarcity. Resources — time, money, land, raw materials — are finite. Wants are not. Every choice, therefore, has a cost: not just the money paid, but the best alternative you gave up. That foregone alternative is the opportunity cost, and it is the single most important concept in all of economics.
Here is a classroom analogy that makes this concrete. You have ₹200 and you can either buy a textbook or go to a movie. If you buy the textbook, the opportunity cost is the movie experience you gave up — not the ₹200 (which is the explicit cost). If someone asks "why is opportunity cost not just the price paid?", the answer is: price is what you spend, opportunity cost is what you sacrifice.
From scarcity and opportunity cost, two fundamental questions emerge:
SSC CGL GK questions from microeconomics almost always fall into three buckets: (a) definitional — "what is X called?"; (b) classification — "is good Y normal, inferior, or Giffen?"; (c) application — deriving a monopolist's price or a consumer's optimal bundle. You need clean definitions and one or two numerical frameworks. The pages ahead give you exactly that.
The Law of Demand states: ceteris paribus (all other things equal), when the price of a good rises, the quantity demanded falls, and vice versa. The demand curve, therefore, slopes downward from left to right.
Why? Two reasons:
Both effects typically reinforce each other, producing lower quantity demanded at higher prices.
Exceptions to the Law of Demand — these are SSC exam favourites:
| Good Type | Behaviour | Demand Curve | |---|---|---| | Normal good | Demand rises with income | Downward sloping | | Inferior good | Demand falls with income | Downward sloping | | Giffen good | Demand rises as price rises | Upward sloping | | Veblen good | Demand rises as price rises (status signal) | Upward sloping |
A Giffen good is a special inferior good where the income effect is so large that it dominates the substitution effect. Classic textbook example: coarse grain (जौ या मोटा अनाज) for very poor households. When its price rises, these households are so much poorer in real terms that they cannot afford anything better — so they buy even more of the cheap grain. Result: price up, demand up. Upward-sloping demand curve.
A Veblen good looks similar numerically but the mechanism is entirely different — prestige and status, not income effect. Luxury watches, designer bags. Do not confuse the two in the exam.
| Income rises | Good type | |---|---| | Demand rises | Normal good | | Demand falls | Inferior good |
Complementary goods are consumed jointly (petrol and cars, tea and sugar). When the price of one rises, demand for both falls — the cross-price effect is negative.
Substitute goods compete with each other (tea and coffee). When the price of one rises, demand for the other rises — the cross-price effect is positive.
Utility is the satisfaction a consumer derives from consuming a good. It is subjective and measured in imaginary units called "utils".
Total Utility (TU): total satisfaction from consuming n units.
Marginal Utility (MU): additional satisfaction from consuming one more unit. MU = ΔTU / ΔQ.
Law of Diminishing Marginal Utility: as you consume more and more units of the same good (holding everything else constant), MU falls. The 1st cup of chai is bliss; the 5th is barely welcome; the 10th might be negative.
Consumer Equilibrium (Cardinal Approach): a consumer spending income on two goods X and Y is in equilibrium when:
This is the Law of Equi-marginal Utility — spread spending until the last rupee spent on each good gives equal marginal utility.
An indifference curve shows all combinations of two goods that give the consumer the same total utility. Key properties:
The Marginal Rate of Substitution (MRS) is the rate at which the consumer is willing to trade one good for another while staying on the same indifference curve. MRS = -ΔY/ΔX = MUx/MUy.
The budget line shows all affordable combinations of two goods given income and prices. Its equation: P_X \cdot X + P_Y \cdot Y = M where M is income. The slope of the budget line is -P_X / P_Y.
Consumer optimum: where the budget line is tangent to the highest attainable indifference curve. At that point: MRS = P_X / P_Y.
If U = X^a \cdot Y^b, optimal demands are:
This is the formula for Cobb-Douglas (also called the standard form in Indian university economics). SSC CGL has tested this directly. The consumer allocates fraction a/(a+b) of income to good X and fraction b/(a+b) to good Y.
| Structure | Sellers | Price Control | Example | |---|---|---|---| | Perfect Competition | Many | None (price taker) | Agricultural markets | | Monopolistic Competition | Many | Slight | Restaurants | | Oligopoly | Few | Significant | Telecom, airlines | | Monopoly | One | High | Railways (historically) | | Monopsony | Many sellers, ONE buyer | Buyer's power | Sole employer in a town |
Monopolist's profit-maximising rule: Set MR = MC.
For a linear demand P = a - bQ: TR = aQ - bQ^2, so MR = a - 2bQ. The MR curve has twice the slope of the demand curve.
Both Giffen and Veblen goods have upward-sloping demand curves, but the causes are different. Remember G-I-N-V: Giffen = Income effect (poor households, necessity), Veblen = Vanity (prestige goods, luxury). Examiners love planting "Giffen" in options when the question describes a luxury good. Checking the income bracket of the consumer eliminates the wrong choice in under 5 seconds vs. rereading both definitions (~30 seconds).
For any linear demand curve P = a - bQ, MR = a - 2bQ. The intercept is the same; the slope is exactly double. So if demand is P = 100 - 2Q, MR = 100 - 4Q — no derivation needed. This reduces a monopoly profit-max problem from 5 steps (derive TR, derive MR, set equal, solve) to 2 steps (write MR by doubling slope, set equal to MC). Time savings: ~40 seconds per problem.
For U = X^a \cdot Y^b, the consumer spends exactly fraction a/(a+b) of income on X and b/(a+b) on Y. When a = b = 0.5, that is a 50-50 income split. So if income is ₹360 and P_X = 4, spending on X = ₹180, units of X = 180/4 = 45. No partial derivatives needed. This takes the standard method from 6 algebraic steps down to 2 arithmetic steps.
The question will say "income increases, demand for good Z [increases/decreases]." If increases → Normal. If decreases → Inferior. That is literally it. Do not overthink. Giffen is a subset of inferior (inferior + price rise causes demand rise). So Giffen only appears when the question also mentions price, not just income. Classify in under 3 seconds; standard rereading of all four options takes ~20 seconds.
Cross-price effect: "price of A rises, demand for B [rises/falls]." Rises → Substitutes (they replace each other). Falls → Complements (they go together). The word "complement" literally means "complete" — the goods complete each other, so when one is less demanded, so is the other. One-second mental check replaces 15-second re-reading of definitions.
When a microeconomics question appears in the SSC CGL GK section, run this decision tree:
Step 1 — Is it definitional or numerical?
Step 2 — What is the numerical type?
a/(a+b), divide by price.MUx/Px = MUy/Py. If not, the consumer should reallocate.Step 3 — Eliminate outliers first. In classification questions (normal/inferior/Giffen/Veblen), eliminate the structurally impossible options first. If the question is about income change only, Giffen is irrelevant (it requires a price-demand relationship). Eliminate it immediately, then choose between normal and inferior based on the direction of demand change.
Keep your GK answers under 30 seconds. These are not calculation-heavy — they reward clean definition recall and fast classification.
Why this question: Tests whether you can identify the Law of Demand by its exact description — inverse price-quantity relationship, ceteris paribus.
Solving path: The phrase "price rises, demand falls, all other factors constant" is the textbook definition of the Law of Demand. "Law of Diminishing Returns" is a production concept (not demand). "Law of Supply" is the opposite direction (price rises, supply rises). "Law of Equi-marginal Utility" is about spending allocation across goods, not price-quantity inverse relation. Eliminate all three, land on Law of Demand.
Why this question: Normal vs. inferior good classification — the most common good-type question in CGL GK.
Solving path: Income rises, demand rises — that is the definition of a Normal good. Inferior good would show demand falling when income rises. Giffen good requires a price-demand context (not income-demand). Substitute good is about cross-price relationships, not income. Answer: Normal good, in under 5 seconds.
Why this question: Giffen good demand curve shape — a direct recall question but one that trips candidates who confuse Giffen with a normal downward-sloping curve.
Solving path: Giffen good violates Law of Demand — price rises, quantity demanded rises. On a standard Price (Y-axis) vs. Quantity (X-axis) graph, that means as you move up (higher price), you also move right (higher quantity). That is an upward-sloping curve. Perfectly vertical = perfectly inelastic (necessities with zero substitute, not Giffen). Perfectly horizontal = perfectly elastic. Downward-sloping is the normal case. Answer: Upward sloping.
Why this question: Cobb-Douglas utility optimisation — the single most calculation-intensive microeconomics PYQ type in CGL.
Solving path: Use the income-split shortcut. a = b = 0.5, so income split is 50-50. Income = ₹360, so spending on X = ₹180. P_X = ₹4. Units of X = 180/4 = 45. Done in two arithmetic steps. Do not set up Lagrangians or partial derivatives in the exam hall.
Why this question: Market structure identification — one seller, many buyers. Classic definition question.
Solving path: "One seller, many buyers" = Monopoly. Perfect competition = many sellers + many buyers. Oligopoly = few large sellers. Monopsony = many sellers, ONE buyer (the mirror image of monopoly on the buying side). The trap option is Monopsony — note it is about the buyer side. Answer: Monopoly.
Why this question: Complementary vs. substitute goods — cross-price demand relationship.
Solving path: "Price of A rises → demand for A falls → demand for B also falls." Both fall together. That is the signature of complementary goods — they are consumed jointly. If B's demand had risen when A's price rose, they would be substitutes. Giffen and inferior are about price-quantity or income-quantity relationships, not cross-price. Answer: Complementary goods.
Why this question: Monopoly pricing via MR = MC — the standard numerical question type.
Solving path: Demand: P = 100 - 2Q. MR = 100 - 4Q (double the slope of demand). Set MR = MC: 100 - 4Q = 20 → 4Q = 80 → Q = 20. Plug back: P = 100 - 2(20) = 100 - 40 = ₹60. Check options: Q = 20, P = ₹60. Done in under 60 seconds using the slope-doubling shortcut.
Confusing Giffen and Veblen goods. Both have upward-sloping demand curves, but the cause is different. Giffen = income effect dominates for an inferior necessity (poor consumer). Veblen = prestige/status (rich consumer). If the question says "luxury" or "status symbol," it is Veblen, not Giffen.
Treating Giffen as a separate category from inferior. A Giffen good is always an inferior good — it is a specific subset. All Giffen goods are inferior, but not all inferior goods are Giffen. Statements like "Giffen goods are not inferior" are false and appear as trap answer choices.
Confusing Monopsony with Monopoly. Monopoly = one seller. Monopsony = one buyer. The "mono" prefix is the same, but the market side differs. If the question says "one buyer," the answer is Monopsony, not Monopoly.
Writing MR with the same slope as demand. For linear demand P = a - bQ, MR = a - 2bQ. The slope of MR is 2b, not b. Getting this wrong makes Q and P both wrong in monopoly problems.
Applying Law of Equi-marginal Utility to price questions. This law is about allocating a budget across multiple goods to maximise utility. It is not about how demand changes with price. Do not invoke it when the question is about the price-quantity relationship.
Ignoring ceteris paribus in demand questions. The Law of Demand holds only when all other factors (income, tastes, prices of related goods) are held constant. If the question changes income simultaneously with price, the Law of Demand result may be overridden. Read the question carefully for what is being held constant.