Paper I — Q1
Answer the following questions in about 150 words each: (a) Compare and contrast Marshallian and Walrasian approaches of the…
Answer the following questions in about 150 words each: Compare and contrast Marshallian and Walrasian approaches of the stability in equilibrium. 10 marks
Using generalised Lorenz dominance show that lower inequality represents a higher social welfare state. 10 marks
Examine the relationship between business cycle and changes in autonomous expenditure. 10 marks
Does government borrowing always crowd out the private investment ? Illustrate. 10 marks
The slope of the IS schedule will become steeper if the government reduces the rate of proportional tax but will not change at all if the government reduces the level of a lump sum tax. True or false ? Explain. 10 marks
हिंदी में प्रश्न पढ़ें
निम्नलिखित प्रत्येक प्रश्न का उत्तर लगभग 150 शब्दों में दीजिए : संतुलन में स्थिरता के मार्शलीयन तथा वालरासीयन दृष्टिकोण की तुलना करें एवं अन्तर प्रदर्शित करें । (10 अंक)
सामान्यीकृत लॉरेंज प्रभुत्व का प्रयोग करते हुए दर्शाइए कि निम्नतर असमानता एक उच्चतर सामाजिक कल्याण की स्थिति को व्यक्त करती है । (10 अंक)
व्यापार चक्र एवं स्वायत्त-व्यय में परिवर्तन के मध्य स्थित सम्बन्ध का परीक्षण कीजिए । (10 अंक)
क्या सरकारी-उधार निजी-निवेश के होने को सदैव रोकता है ? उदाहरण देकर समझाइए । (10 अंक)
यदि सरकार अनुपाती कर की दर को घटा दे तो IS वक्र अधिक खड़ी ढाल वाला हो जायेगा किन्तु यदि एकमुश्त कर का स्तर घटाया जाये तो IS वक्र का ढाल परिवर्तित नहीं होगा । सत्य अथवा असत्य ? समझाइए । (10 अंक)
Model answer
Written by UPSC Answer Check against this question's marking rubric, to the 150-word length. UPSC does not publish answers for Mains — this is one way to score well, not an official key.
(a) Marshallian and Walrasian stability. Marshallian stability is a partial-equilibrium test. In one market, price adjusts to excess demand: if demand exceeds supply, price rises; if supply exceeds demand, price falls. Formally, dp/dt = λD(p), with λ>0; equilibrium is locally stable when the excess-demand curve cuts the price axis from above, so a small price deviation generates a restoring force. The analysis holds other prices fixed and assumes the market can clear independently. Walrasian stability is a general-equilibrium test. All commodity prices adjust simultaneously through a tâtonnement process, with no trade off equilibrium. The vector of excess demands Z(p) determines dp/dt, and stability requires that the system of price equations converge to p* from nearby initial prices; locally this requires the eigenvalues of the excess-demand Jacobian to have negative real parts. The contrast is therefore between one-price, market-by-market adjustment and all-price, system-wide adjustment, with different assumptions about speed and interdependence.
(b) Generalised Lorenz dominance and welfare. The Lorenz curve plots cumulative income share against cumulative population share; the generalized Lorenz curve multiplies it by mean income μ, so G(p)=μL(p). Distribution A dominates B by generalized Lorenz dominance if G_A(p)≥G_B(p) for all p, with strict inequality somewhere, implying a higher or equal mean and no crossing. This dominance is welfare-relevant because any social welfare function that is increasing in income, symmetric, and concave (inequality-averse) ranks A at least as high as B. Atkinson’s theorem formalises this: for a given inequality-aversion parameter ε, welfare can be written as μ(1-I(ε)), where I(ε) is the Atkinson index; a higher generalized Lorenz curve lowers I(ε) and raises welfare. Thus, at the same mean, a lower-inequality distribution has a higher Lorenz and generalized Lorenz curve and yields higher welfare for all inequality-averse preferences; if it also has a higher mean, the welfare gain is unambiguous. Hence lower inequality, when it does not reduce the mean, represents a higher social welfare state.
(c) Business cycle and autonomous expenditure. Autonomous expenditure Aₜ is the impulse that starts a cycle. In the Samuelson-Hicks linear model, output is Yₜ=Cₜ+Iₜ+Aₜ, with consumption Cₜ=cYₜ₋₁ and investment Iₜ=v(Yₜ₋₁-Yₜ₋₂). Substitution gives Yₜ=(c+v)Yₜ₋₁-vYₜ₋₂+Aₜ. A rise in Aₜ raises income through the multiplier, 1/(1-c), while the accelerator makes investment respond to the change in output, so the initial demand shock is amplified and fed back into later periods; a fall in Aₜ reverses the process. The homogeneous characteristic equation is λ²-(c+v)λ+v=0. When (c+v)²<4v, the roots are complex and output fluctuates cyclically; the modulus of the roots determines whether cycles are damped, constant, or explosive. If roots are real, adjustment is monotonic or non-cyclical. Because the model is linear, the amplitude is proportional to the autonomous shock, and cycles arise from parameter values rather than non-linearity. Thus autonomous expenditure changes are the exogenous trigger, while the multiplier-accelerator interaction converts them into business-cycle dynamics.
(d) Crowding out. Government borrowing does not always crowd out private investment. In the IS-LM framework, a deficit-financed rise in government spending shifts IS right; if the LM curve is upward sloping, the new equilibrium has a higher interest rate, which reduces private investment. The size of crowding out depends on the slope of LM and the interest sensitivity of investment. With a vertical LM curve, the interest rate rises enough to offset the entire increase in government spending, giving full crowding out. With a horizontal LM curve, as in a liquidity trap, the interest rate does not rise, so crowding out is minimal. In a recession with idle capacity, public investment can also crowd in by improving infrastructure, raising expected returns, or increasing confidence. Ricardian equivalence offers a further qualification: if households anticipate future taxes and save more, borrowing may not raise interest rates. Hence crowding out is a tendency, not an identity; it is strongest near full employment and tight monetary conditions, as when market borrowings tighten liquidity. In India, RBI liquidity conditions shape this effect.
(e) IS slope and taxes. True in the algebraic IS equation, where slope is the income response to interest-rate changes. Let C=a+c(Y-T), T=T0+tY, and I=I0-br. Then Y=a+c(Y-T0-tY)+I0-br+G, so Y[1-c(1-t)]=a-cT0+I0+G-br. Hence dY/dr=-b/[1-c(1-t)]. A reduction in the proportional tax rate t lowers 1-c(1-t), raising the absolute value of dY/dr and increasing the multiplier 1/[1-c(1-t)]; the IS schedule therefore becomes steeper in the Y-r algebra. A reduction in lump-sum tax T0 changes only the intercept a-cT0+I0+G, shifting IS without altering dY/dr. In the conventional r-Y diagram, the same algebra is drawn as a flatter IS, but the statement’s slope claim is correct when slope is the coefficient of r in the income equation.
What "Compare and contrast" is asking you to do
Both halves, visibly separated, usually because the two are routinely conflated: similarities across the stated dimensions, then differences across those same dimensions. The longer form is an instruction that the differences must not be folded into the similarities.
Structure that answers it
Dimensions fixed → similarities across them → differences across them → why the pair gets confused and what in fact separates it
Where marks are lost
One half done in a page and the other in three lines. Marks are allotted to each half separately, so the weaker half is lost however strong the other is.
How this answer will be evaluated
Approach
Framework: IS-LM / General Equilibrium / Welfare Economics. (a) compare: paired headings or table > key differences > significance > conclusion | (b) justify: claim > 3-4 reasons > evidence > conclusion | (c) examine: intro > how/why with reasoning > evidence > conclusion | (d) comment: context > arguments both sides > judgment > close | (e) explain: definition/context > points in order > small example > short close Full marks: Rigorous derivation, correct diagrams, clear distinction of concepts.
Key points expected
- Marshallian: price adjustment, excess demand
- Walrasian: quantity adjustment, excess supply
- Stability condition: slope of D vs S
- Diagram: Price vs Quantity axes
- Definition of Lorenz curve dominance
- Link to social welfare function (SWF)
- Diagram: Cumulative % income vs population
- Logic: Dominance implies higher welfare
Evaluation rubric
Each sub-part is marked on its own, against the marks and word limit printed on the paper.
- (a) Contrast Marshallian (partial) vs Walrasian (general) stability mechanisms. 10 marks · 150 words
compare— paired headings or table → key differences → significance → conclusion
Must cover
- Marshallian: price adjustment, excess demand
- Walrasian: quantity adjustment, excess supply
- Stability condition: slope of D vs S
- Diagram: Price vs Quantity axes
Loses marks
- Confusing partial with general equilibrium
- Verbal description without diagram
Earns more
- Mention of tâtonnement process
- Reference to Walras' Law
Extra mark
- Reference to Samuelson's critique
- (b) Prove lower inequality implies higher welfare via Lorenz dominance. 10 marks · 150 words
justify— claim → 3-4 reasons → evidence → conclusion
Must cover
- Definition of Lorenz curve dominance
- Link to social welfare function (SWF)
- Diagram: Cumulative % income vs population
- Logic: Dominance implies higher welfare
Loses marks
- Failing to link curve to welfare
- Incorrect Lorenz curve plotting
Earns more
- Mention of Gini coefficient
- Reference to Rawlsian maximin
Extra mark
- Reference to Sen's capability approach
- (c) Analyze link between business cycles and autonomous expenditure. 10 marks · 150 words
examine— intro → how/why with reasoning → evidence → conclusion
Must cover
- Multiplier effect on equilibrium Y
- Autonomous expenditure as shock
- Diagram: IS-LM or AD-AS shift
- Expansion vs contraction phases
Loses marks
- Ignoring the multiplier mechanism
- Static analysis without cycle context
Earns more
- Mention of investment volatility
- Reference to Keynesian multiplier
Extra mark
- Reference to specific Indian budget data
- (d) Evaluate if government borrowing always crowds out private investment. 10 marks · 150 words
comment— context → arguments both sides → judgment → close
Must cover
- Mechanism: Interest rate rise (r)
- Condition: Full employment vs recession
- Diagram: IS-LM shift showing r change
- Distinction: Full vs partial crowding out
Loses marks
- Asserting 'always' without conditions
- Ignoring interest rate channel
Earns more
- Mention of liquidity trap
- Reference to Ricardian Equivalence
Extra mark
- Reference to recent Indian bond yields
- (e) Verify statement on IS slope vs proportional vs lump sum tax. 10 marks · 150 words
explain— definition/context → points in order → small example → short close
Must cover
- Derivation of IS slope formula
- Effect of t (proportional) on slope
- Effect of T (lump sum) on intercept
- Conclusion: Statement is True
Loses marks
- Confusing slope with intercept
- Failing to derive the formula
Earns more
- Mathematical derivation of slope
- Diagram showing parallel shift vs rotation
Extra mark
- Reference to specific tax policy change
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Write your answer and it is marked point by point against the model answer above — what you covered, what you missed, what you got wrong.
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