IIT JAM Economics: Micro, Macro and Applied Statistics
IIT JAM EN tests microeconomic choice, market structure, macroeconomics, national income, money and inflation, plus statistical and econometric reasoning. The paper rewards clear definitions, correct elasticity and multiplier arithmetic, and interpretation of models rather than slogan-level answers.
Core rules and concepts
- Consumer choice: the budget constraint is PxX + PyY = M; utility is maximized where MRS = Px/Py, subject to the budget.
- Elasticity: price elasticity of demand ε = (dQ/dP)(P/Q); use the midpoint formula for arc elasticity. Elasticity is not the slope of the demand curve.
- Market structure: perfect competition sets P = MC in equilibrium; a monopolist sets MR = MC and creates deadweight loss.
- National income: GDP = C + I + G + (X − M); nominal GDP uses current prices, real GDP uses base-year prices; the GDP deflator is nominal/real × 100.
- Macro policy: IS–LM links goods and money markets; fiscal and monetary policy shift the relevant curves; inflation and unemployment trade-offs depend on expectations.
- Econometrics: OLS minimizes the sum of squared residuals; Gauss–Markov requires linearity, exogeneity, homoskedasticity and no perfect collinearity for BLUE.
Worked example
Demand is Q = 100 − 2P. At P = 20, Q = 60. The derivative is dQ/dP = −2, so point elasticity is ε = (−2)(20/60) = −2/3. Since |ε| < 1, demand is inelastic at that point: a 1% price rise reduces quantity by about 0.67%.
Traps that cost marks
Do not confuse a movement along a demand curve with a shift of the curve. Keep nominal and real variables separate. Do not treat GDP as including intermediate goods. Correlation in a regression is not causation, and a high R² does not prove a model is correctly specified.
Key points
- Point elasticity uses (dQ/dP)(P/Q).
- Monopoly equilibrium is MR = MC, not P = MC.
- Real GDP isolates quantity changes from price changes.
- IS–LM links interest rate, output and policy shifts.
- OLS requires exogeneity for unbiased causal interpretation.