This MCQ module is based on: Inflationary/Deflationary Gap & Exercises
TOPIC 11 OF 17
Inflationary/Deflationary Gap & Exercises
🎓 Class 12
Economics
CBSE
Theory
Chapter 4 — Determination of Income and Employment
⏱ ~28 min
🌐 Language: [gtranslate]
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Inflationary & Deflationary Gaps, Policy Measures and Income Determination Exercises
Equilibrium income is whatever income makes plans consistent — but it need not be a good equilibrium. The economy can rest at an output below full employment (idle workers, idle machines) or be pushed by demand beyond full employment (rising prices). The first situation is called deficient demand; the second, excess demand. In Part 3 we measure these gaps, walk through the fiscal and monetary tools that close them, and finish with full model answers to every NCERT exercise — including the famous Q5 numerical and the Paradox of Thrift question.
4.8 Equilibrium ≠ Full Employment
The equilibrium level of output is determined by AD = AS. But the level of output that fully employs all factors of production — labour, machines, land, raw materials — is given by the economy's productive capacity. We call that special level the full-employment level of income?, denoted Yf. Equilibrium income Y* and full-employment income Yf need not coincide.
📌 Two Key Possibilities
• If Y* < Yf — the equilibrium output is less than the full-employment level. There is unemployment of factors and falling prices in the long run. This is the situation of deficient demand.• If Y* > Yf — the equilibrium "demand" output exceeds what the economy can produce at full employment. There are no idle factors to draw on, so the extra demand pushes prices up, not output. This is excess demand, leading to inflation in the long run.
4.9 Excess Demand & the Inflationary Gap
An excess demand? situation arises when ex-ante aggregate demand at the full-employment level of output exceeds aggregate supply at that same level. The amount by which AD exceeds the full-employment AS is called the inflationary gap?. Since output cannot rise beyond full employment, the excess demand pushes the price level up.
📐 Inflationary Gap — Definition
Inflationary Gap = ADat Yf − ASat Yf = ADat Yf − YfThis is the vertical distance, at the full-employment level Yf, between the AD line and the 45° AS line. It is the amount by which planned spending exceeds the maximum the economy can produce.
The Inflationary Gap — AD Above Yf
Bloom: L4 Analyse4.9.1 Causes of an Inflationary Gap
- Sharp rise in autonomous investment (a boom in business confidence).
- Big increase in government expenditure (war, large stimulus during a boom).
- Reduction in personal income taxes that boosts consumption.
- Sudden rise in exports (foreign demand pulled in).
- Cheap-money policy that swells lending and induced investment beyond capacity.
4.9.2 Removing an Inflationary Gap — Contractionary Policy
The cure is to push AD down until it just touches the 45° line at Yf. The two policy instruments are fiscal policy? (run by the government, dealing with G and T) and monetary policy? (run by the RBI, dealing with money supply and interest rates).
Reduce G
Cut government expenditure on goods, services and projects to lower the autonomous component of AD directly.
Raise Taxes (T)
Higher direct taxes shrink disposable income, lowering induced consumption and aggregate demand.
Raise CRR / SLR
RBI raises the cash reserve ratio and statutory liquidity ratio — banks have less to lend, so credit and induced investment fall.
Raise Repo Rate
RBI hikes the repo rate; bank lending rates rise; investment falls; AD line shifts down. Open-market sale of bonds also drains liquidity.
4.10 Deficient Demand & the Deflationary Gap
A deficient demand? situation is the mirror image: ex-ante aggregate demand at the full-employment level of output falls short of full-employment supply. The amount by which AD lies below the 45° line at Yf is called the deflationary gap?. Output and employment fall below capacity; idle workers and idle machines appear; in the long run, prices fall.
📐 Deflationary Gap — Definition
Deflationary Gap = Yf − ADat YfThis is the vertical distance, at the full-employment level Yf, by which the 45° AS line lies above the AD line.
The Deflationary Gap — AD Below Yf
Bloom: L4 Analyse4.10.1 Causes of a Deflationary Gap
- Sharp fall in autonomous investment (loss of business confidence).
- Cut in government expenditure (austerity, end of stimulus programme).
- Higher direct taxes that shrink disposable income.
- Fall in exports (global slowdown).
- Tight money policy that raises interest rates and chokes off investment.
- Rise in MPS / fall in MPC (paradox of thrift, fear-driven precautionary saving).
4.10.2 Removing a Deflationary Gap — Expansionary Policy
The cure is to push AD up until it touches the 45° line at Yf. Each policy lever is the mirror of the contractionary case.
Raise G
Government undertakes new public investment — roads, schools, hospitals — directly raising AD by ΔG, which is then multiplied by k.
Cut Taxes (T)
Lower direct taxes raise households' disposable income, increasing induced consumption and aggregate demand.
Lower CRR / SLR
RBI cuts CRR and SLR; banks now have more loanable funds; cheaper credit lifts induced investment.
Lower Repo Rate
RBI cuts the repo rate; bank lending rates fall; firms invest more; AD line shifts up. Open-market purchase of bonds adds liquidity.
4.10.3 Quantifying the Required Change
📐 Closing the Gap — How Much Stimulus is Needed?
Required ΔAD at Yf = the size of the gap.But the multiplier amplifies any change in autonomous spending. Hence:
ΔĀ required = (Gap size) / k = (Gap size) × (1 − b)Example: gap = ₹100 cr, MPC = 0.8 → multiplier k = 5 → government must inject 100/5 = ₹20 cr of autonomous spending. The other ₹80 cr is generated by induced consumption rounds.
4.11 Quick Comparison — Excess vs Deficient Demand
| Aspect | Excess Demand (Inflationary) | Deficient Demand (Deflationary) |
|---|---|---|
| Definition | AD > AS at Yf | AD < AS at Yf |
| Gap Name | Inflationary gap | Deflationary gap |
| Effect on Output | Cannot rise above Yf | Falls below Yf |
| Effect on Prices | Rise (inflation) | Fall in long run (deflation) |
| Effect on Employment | Already at full employment | Unemployment rises |
| Required Policy | Contractionary | Expansionary |
| Fiscal Tools | Cut G; raise T | Raise G; cut T |
| Monetary Tools | Raise repo rate, CRR, SLR; OMO sales | Cut repo rate, CRR, SLR; OMO purchases |
How Multiplier Magnifies a Policy Push
Figure 4.D: For three different MPC values, see how a ₹50 cr injection translates into ΔY. Higher MPC means a steeper multiplier and so a much bigger income response — but also the risk of overshooting Yf into inflation.
LET'S EXPLORE — Identify and Close the Gap
Bloom: L4 Analyse
An economy has C = 100 + 0.75Y, autonomous investment Ī = ₹100 cr, and a full-employment income Yf = ₹1,200 cr. (i) Find the equilibrium income. (ii) Identify the type of gap. (iii) Compute the gap size at Yf. (iv) Find the change in autonomous spending needed to close the gap.
✅ Worked Solution
(i) Ā = 100 + 100 = 200; k = 1/(1 − 0.75) = 4; Y* = 200 × 4 = ₹800 cr. (ii) Y* = 800 < Yf = 1200 → deflationary gap (deficient demand). (iii) AD at Yf: 100 + 0.75(1200) + 100 = 100 + 900 + 100 = ₹1,100 cr. AS at Yf = ₹1,200 cr. Gap = 1200 − 1100 = ₹100 cr. (iv) Required ΔĀ = Gap / k = 100 / 4 = ₹25 cr. Government can raise G by ₹25 cr (or any combination of fiscal and monetary measures whose net autonomous effect is +₹25 cr); the multiplier turns this ₹25 cr into the ₹100 cr ΔY needed.
THINK — Why Both Types of Policy?
Bloom: L5 Evaluate
If the government can simply change G to close any gap, why do central banks also use monetary policy? List three real-world reasons fiscal policy alone is not always enough — and one situation where monetary policy alone may fail.
✅ Discussion Notes
Three reasons fiscal policy is not always enough: (1) Implementation lag — changing budgets, building roads, hiring teachers all take time; recessions strike fast. Monetary policy can be changed in a single RBI committee meeting. (2) Fiscal-deficit constraints — governments with high public debt may be unable to spend more without losing investor confidence. (3) Political pressures — cutting G or raising T to fight inflation is unpopular; a politically independent central bank can act when politicians cannot. One case where monetary policy alone fails: a "liquidity trap" or near-zero interest rates (e.g. Japan in the 1990s, advanced economies after 2008) — when rates are already at zero, further cuts cannot stimulate investment, and only fiscal expansion or unconventional measures can restore demand.
DISCUSS — Indian Episode of Each Gap
Bloom: L5 Evaluate
Use what you have learnt to interpret two real Indian episodes: (a) the period 2010–13, when CPI inflation in India remained near double-digit levels; (b) the period 2020–21 (COVID-19), when growth turned sharply negative. Which sort of gap dominated each period? What policy response did the RBI/Government use, and was it consistent with the textbook prescription?
✅ Discussion Notes
(a) 2010–13: Excess-demand pressures and supply-side bottlenecks combined to produce high inflation. The textbook prescription is contractionary monetary policy. RBI raised the repo rate from around 5% in March 2010 to over 8% by 2013 — exactly aligned with the inflationary-gap response. (b) 2020–21 COVID: Aggregate demand collapsed (lockdowns, fear-driven precautionary saving, the paradox of thrift). The textbook prescription is expansionary policy. RBI cut the repo rate from 5.15% to 4.0% and slashed CRR; the Government rolled out the ₹20 lakh crore "Atmanirbhar Bharat" stimulus package, with large transfers and credit guarantees. Both moves are textbook deflationary-gap policy. (Real-world details — supply shocks, inflation expectations — make the analysis richer, but the underlying gap logic remains.)
4.12 Summary of the Chapter
Key Takeaways — Chapter 4
- The chapter assumes a fixed price level and constant interest rate — the Keynesian short-run setup — and uses the ceteris paribus method.
- Ex-ante values are planned (forward-looking); ex-post values are realised. Equilibrium requires ex-ante AD to equal ex-ante AS; out of equilibrium, the gap appears as unintended inventory accumulation or de-stocking.
- Aggregate demand = C + I (closed without government); = C + I + G (with government); = C + I + G + (X − M) (open).
- The consumption function is C = c̄ + bY: c̄ = autonomous consumption, b = MPC. APC = C/Y; MPC = ΔC/ΔY; MPC + MPS = 1; S = −c̄ + (1 − b)Y.
- The 45° line represents AS in the fixed-price model. Equilibrium: Y* = Ā / (1 − b), equivalently S = I.
- The investment multiplier k = ΔY/ΔĀ = 1/(1 − MPC) = 1/MPS > 1. Every extra rupee of autonomous spending raises income by k rupees through successive consumption rounds.
- Equilibrium income may differ from full-employment income. Y* > Yf = excess demand → inflationary gap → contractionary policy. Y* < Yf = deficient demand → deflationary gap → expansionary policy.
- Fiscal tools: change G and T. Monetary tools: change repo rate, CRR, SLR, OMO operations.
- Paradox of thrift: if the whole economy tries to save more, total savings do not rise — equilibrium income falls and the higher saving ratio is applied to a smaller base.
- Effective demand principle: in the short run with unused resources, aggregate output is determined by aggregate demand alone.
4.13 Key Terms — Quick Glossary
Aggregate Demand (AD)Total ex-ante spending: C + I (+ G + X − M).
Aggregate Supply (AS)Total ex-ante output. In the fixed-price model, AS = Y (the 45° line).
Ex-AntePlanned, intended, forward-looking values.
Ex-PostRealised, actual, after-the-fact values.
Consumption FunctionC = c̄ + bY: planned consumption as a function of income.
Autonomous Consumption (c̄)The intercept; consumption at zero income.
MPC = bMarginal propensity to consume = ΔC/ΔY; slope of consumption function.
APCAverage propensity to consume = C/Y.
MPSMarginal propensity to save = 1 − MPC = ΔS/ΔY.
APSAverage propensity to save = S/Y; APC + APS = 1.
Saving FunctionS = −c̄ + (1 − b)Y, derived from S ≡ Y − C.
Investment Multiplier (k)k = 1/(1 − b) = 1/MPS = ΔY/ΔĀ.
Equilibrium Income (Y*)Y* = Ā/(1 − b); income where AD = AS or S = I.
Full-Employment Output (Yf)Output level at which all factors are fully employed.
Inflationary GapADYf − Yf when AD > Yf; pushes prices up.
Deflationary GapYf − ADYf when AD < Yf; idle factors and falling prices.
Paradox of ThriftRise in MPS lowers Y* without raising aggregate savings.
Effective Demand PrincipleOutput is set by AD when supply is perfectly elastic.
Fiscal PolicyGovernment use of G and T to change AD.
Monetary PolicyCentral-bank use of interest rates and money supply to change AD.
Parametric ShiftChange in a parameter (intercept or slope) of a function — shifts the line up or swings it.
Unintended Inventory InvestmentUnplanned change in stocks when AD ≠ planned output.
4.14 NCERT Exercises — Full Model Answers
Q1. What is marginal propensity to consume? How is it related to marginal propensity to save?
Marginal Propensity to Consume (MPC) is the change in planned consumption per unit change in income: MPC = ΔC / ΔY = b. It measures how much of an extra rupee of income is spent on consumption rather than saved. Generally 0 ≤ MPC ≤ 1.
Relation with MPS: Since income is either consumed or saved (Y ≡ C + S), any change in income must split between change in consumption and change in saving: ΔY = ΔC + ΔS. Dividing by ΔY: 1 = ΔC/ΔY + ΔS/ΔY, hence MPC + MPS = 1, equivalently MPS = 1 − MPC. So when MPC is high (people spend most of any extra income), MPS is low (they save little); and vice versa. In the linear consumption function C = c̄ + bY, the slope b is MPC and (1 − b) is MPS.
Relation with MPS: Since income is either consumed or saved (Y ≡ C + S), any change in income must split between change in consumption and change in saving: ΔY = ΔC + ΔS. Dividing by ΔY: 1 = ΔC/ΔY + ΔS/ΔY, hence MPC + MPS = 1, equivalently MPS = 1 − MPC. So when MPC is high (people spend most of any extra income), MPS is low (they save little); and vice versa. In the linear consumption function C = c̄ + bY, the slope b is MPC and (1 − b) is MPS.
Q2. What is the difference between ex-ante investment and ex-post investment?
Ex-ante investment is the planned or intended investment that producers wish to undertake during a given period — including their planned addition to inventory. It is a forward-looking, plan-based concept used in equilibrium analysis.
Ex-post investment is the actual, realised investment that took place during the period — including any unintended change in inventory because actual sales differed from planned sales. It is a backward-looking, accounting concept used in national income accounts.
Example: A producer plans to add ₹100 worth of goods to inventory (ex-ante I = ₹100). An unexpected demand surge forces her to sell ₹30 from stock; only ₹70 is added to inventory (ex-post I = ₹70). The ₹30 difference is unplanned (unintended) de-stocking. Ex-ante and ex-post investment are equal only when the goods market is in equilibrium.
Ex-post investment is the actual, realised investment that took place during the period — including any unintended change in inventory because actual sales differed from planned sales. It is a backward-looking, accounting concept used in national income accounts.
Example: A producer plans to add ₹100 worth of goods to inventory (ex-ante I = ₹100). An unexpected demand surge forces her to sell ₹30 from stock; only ₹70 is added to inventory (ex-post I = ₹70). The ₹30 difference is unplanned (unintended) de-stocking. Ex-ante and ex-post investment are equal only when the goods market is in equilibrium.
Q3. What do you understand by 'parametric shift of a line'? How does a line shift when its (i) slope decreases, and (ii) its intercept increases?
A parametric shift of a line means a change in one of the parameters (the slope or the intercept) of the line's equation, which causes the line to move on the diagram. For the line Y = a + bX, a is the intercept (Y-axis value at X = 0) and b is the slope.
(i) Slope decreases (b falls): The line becomes flatter. It pivots about its intercept on the Y-axis — the Y-intercept stays fixed, but for any positive X the line is now lower. This is called a downward swing. In Keynesian terms, a fall in MPC swings the AD line downwards (paradox-of-thrift situation).
(ii) Intercept increases (a rises): The line shifts upward in parallel — every point on the line moves up by the same vertical distance equal to the rise in the intercept; the slope is unchanged. In Keynesian terms, a rise in autonomous spending Ā shifts the AD line up in parallel; equilibrium income rises by k × ΔĀ.
(i) Slope decreases (b falls): The line becomes flatter. It pivots about its intercept on the Y-axis — the Y-intercept stays fixed, but for any positive X the line is now lower. This is called a downward swing. In Keynesian terms, a fall in MPC swings the AD line downwards (paradox-of-thrift situation).
(ii) Intercept increases (a rises): The line shifts upward in parallel — every point on the line moves up by the same vertical distance equal to the rise in the intercept; the slope is unchanged. In Keynesian terms, a rise in autonomous spending Ā shifts the AD line up in parallel; equilibrium income rises by k × ΔĀ.
Q4. What is 'effective demand'? How will you derive the autonomous expenditure multiplier when price of final goods and the rate of interest are given?
Effective demand is the level of aggregate demand that becomes equal to aggregate supply in equilibrium — i.e. the AD that the economy is actually able to realise as output and income, given a fixed price level and a fixed rate of interest. The effective demand principle states that under these conditions, aggregate output is determined solely by the level of aggregate demand.
Derivation of the autonomous expenditure multiplier:
Start with the equilibrium condition AD = AS, where AS = Y and AD = c̄ + Ī + bY (in the simplest two-sector model).
Y = c̄ + Ī + bY
Y(1 − b) = c̄ + Ī = Ā
Y* = Ā / (1 − b) … (★)
Now suppose autonomous expenditure Ā rises by ΔĀ. The new equilibrium income is Y* + ΔY = (Ā + ΔĀ)/(1 − b). Subtracting the original (★):
ΔY = ΔĀ / (1 − b)
k = ΔY / ΔĀ = 1 / (1 − b) = 1 / MPS
This k is the autonomous expenditure multiplier. Because 0 < b < 1, k > 1: an extra rupee of autonomous spending raises income by more than one rupee through successive rounds of induced consumption.
Derivation of the autonomous expenditure multiplier:
Start with the equilibrium condition AD = AS, where AS = Y and AD = c̄ + Ī + bY (in the simplest two-sector model).
Y = c̄ + Ī + bY
Y(1 − b) = c̄ + Ī = Ā
Y* = Ā / (1 − b) … (★)
Now suppose autonomous expenditure Ā rises by ΔĀ. The new equilibrium income is Y* + ΔY = (Ā + ΔĀ)/(1 − b). Subtracting the original (★):
ΔY = ΔĀ / (1 − b)
k = ΔY / ΔĀ = 1 / (1 − b) = 1 / MPS
This k is the autonomous expenditure multiplier. Because 0 < b < 1, k > 1: an extra rupee of autonomous spending raises income by more than one rupee through successive rounds of induced consumption.
Q5. Measure the level of ex-ante aggregate demand when autonomous investment and consumption expenditure (Ā) is ₹50 crore, and MPS is 0.2 and level of income (Y) is ₹4,000 crore. State whether the economy is in equilibrium or not (cite reasons).
Given: Ā = 50 cr; MPS = 0.2 → MPC = b = 1 − 0.2 = 0.8; Y = 4,000 cr.
Step 1 — Compute AD at Y = 4,000:
AD = Ā + bY = 50 + 0.8 × 4,000 = 50 + 3,200 = ₹3,250 crore.
Step 2 — Test equilibrium condition (AD = Y?):
AD = 3,250 ≠ Y = 4,000 → the economy is NOT in equilibrium.
Reason: Aggregate Demand (₹3,250 cr) falls short of Aggregate Supply (₹4,000 cr) by ₹750 cr. There is excess supply: producers planned to produce ₹4,000 cr of final goods but spenders are willing to buy only ₹3,250 cr worth. The unsold ₹750 cr piles up as unintended inventory accumulation. In response, producers will cut planned output in subsequent periods until equilibrium is restored.
Where would equilibrium actually lie?
Y* = Ā / (1 − b) = 50 / 0.2 = ₹250 crore. The economy is far above equilibrium income at the moment; output will fall toward ₹250 cr.
Step 1 — Compute AD at Y = 4,000:
AD = Ā + bY = 50 + 0.8 × 4,000 = 50 + 3,200 = ₹3,250 crore.
Step 2 — Test equilibrium condition (AD = Y?):
AD = 3,250 ≠ Y = 4,000 → the economy is NOT in equilibrium.
Reason: Aggregate Demand (₹3,250 cr) falls short of Aggregate Supply (₹4,000 cr) by ₹750 cr. There is excess supply: producers planned to produce ₹4,000 cr of final goods but spenders are willing to buy only ₹3,250 cr worth. The unsold ₹750 cr piles up as unintended inventory accumulation. In response, producers will cut planned output in subsequent periods until equilibrium is restored.
Where would equilibrium actually lie?
Y* = Ā / (1 − b) = 50 / 0.2 = ₹250 crore. The economy is far above equilibrium income at the moment; output will fall toward ₹250 cr.
Q6. Explain 'Paradox of Thrift'.
Statement: The Paradox of Thrift states that when every household in the economy decides to save a higher fraction of its income (i.e. MPS rises), the total amount of saving in the economy does not rise — it either remains unchanged or actually falls. What is true for an individual is not true for the economy as a whole; this is a classic fallacy of composition.
How it works (with NCERT numbers):
Suppose initially Ā = 50 and MPC = b = 0.8. Equilibrium income Y₁* = 50 / (1 − 0.8) = 250. At this Y, S = Y − C = 250 − (40 + 0.8 × 250) = 10.
Now everyone becomes more thrifty: MPC falls to 0.5 (MPS rises to 0.5). The new equilibrium income is Y₂* = 50 / (1 − 0.5) = 100. At the new Y, S = 100 − (40 + 0.5 × 100) = 100 − 90 = 10. Total savings remain at ₹10 — exactly the same as before.
Why? A higher desire to save reduces consumption, which lowers AD. AD line swings down. Excess supply emerges. Producers cut output. Income falls. The higher saving ratio is now applied to a much smaller income base. The two effects exactly offset: total saving is unchanged.
Significance: The paradox warns policy-makers that exhortations to "save more" during a recession can be self-defeating. In a downturn, what is needed is more spending to restart the multiplier; rising precautionary saving deepens the recession.
How it works (with NCERT numbers):
Suppose initially Ā = 50 and MPC = b = 0.8. Equilibrium income Y₁* = 50 / (1 − 0.8) = 250. At this Y, S = Y − C = 250 − (40 + 0.8 × 250) = 10.
Now everyone becomes more thrifty: MPC falls to 0.5 (MPS rises to 0.5). The new equilibrium income is Y₂* = 50 / (1 − 0.5) = 100. At the new Y, S = 100 − (40 + 0.5 × 100) = 100 − 90 = 10. Total savings remain at ₹10 — exactly the same as before.
Why? A higher desire to save reduces consumption, which lowers AD. AD line swings down. Excess supply emerges. Producers cut output. Income falls. The higher saving ratio is now applied to a much smaller income base. The two effects exactly offset: total saving is unchanged.
Significance: The paradox warns policy-makers that exhortations to "save more" during a recession can be self-defeating. In a downturn, what is needed is more spending to restart the multiplier; rising precautionary saving deepens the recession.
Additional Practice — Numerical & Theoretical
Q7 (Practice). If the consumption function is C = 80 + 0.6Y and Ī = 40, find the equilibrium income, equilibrium consumption, equilibrium saving, and the multiplier.
Ā = 80 + 40 = 120; (1 − b) = 0.4; Y* = 120 / 0.4 = 300. Equilibrium consumption C* = 80 + 0.6 × 300 = 80 + 180 = 260. Equilibrium saving S* = Y* − C* = 300 − 260 = 40 = Ī (S = I confirmed). Multiplier k = 1/(1 − 0.6) = 2.5. Verification by AD: AD at Y = 300 is C + I = 260 + 40 = 300 = Y ✓.
Q8 (Practice). In an economy MPC = 0.75 and full-employment income is ₹4,000 cr. Current equilibrium income is ₹3,200 cr. Identify the gap, compute its size, and state how much extra autonomous government spending is required to close it.
Y* = 3,200 < Yf = 4,000 → deflationary gap (deficient demand). Required ΔY = 4,000 − 3,200 = ₹800 cr. Multiplier k = 1/(1 − 0.75) = 4. Therefore required ΔĀ = ΔY / k = 800 / 4 = ₹200 cr. The government must inject ₹200 cr of additional autonomous spending; the multiplier turns it into the ₹800 cr of additional income needed to reach full employment. Equivalently, the deflationary gap (vertical distance) at Yf is also ₹200 cr.
Q9 (Practice). MPC = 0.8 and the inflationary gap at Yf = ₹6,000 cr is ₹150 cr. By how much should the government cut its expenditure to restore full-employment equilibrium?
Inflationary gap = ₹150 cr means AD at Yf exceeds AS by ₹150 cr. The multiplier is k = 1/(1 − 0.8) = 5. To pull AD down by exactly ₹150 cr we must reduce autonomous spending by ΔĀ = 150 cr only at the autonomous level — but the gap measures the vertical distance, which is the autonomous discrepancy itself. So the government must cut G by ₹150 cr. (Alternatively, raise direct taxes by an amount that reduces autonomous consumption by ₹150 cr — i.e. ΔT = 150/MPC = 187.5 cr.) Verification: ΔĀ = −150 → ΔY = 5 × (−150) = −750, exactly the income reduction needed to drag the economy down to Yf from its excess-demand trajectory.
Q10 (Practice). State four monetary measures the RBI can take to combat a deflationary gap. For each, briefly explain the channel through which AD rises.
(i) Reduce the repo rate: Banks borrow more cheaply from RBI; their lending rates fall; firms borrow more for investment and households for durables/housing; the I and C components of AD rise. (ii) Reduce the CRR: Banks have more loanable reserves; credit expands; investment rises. (iii) Reduce the SLR: Banks free up assets from government bonds for commercial lending; same channel. (iv) Conduct open-market purchases (OMO buying): RBI buys government bonds in the open market, releasing cash into the banking system; banks lend more; AD rises. Each measure shifts the AD line upwards, multiplied by k = 1/MPS to give a larger ΔY.
Q11 (Practice). Distinguish, with examples, between an autonomous variable and an induced variable in the Keynesian model.
An autonomous variable does not depend on income within the model — its value is set by factors outside the model, such as policy decisions, expectations or technology. Examples: autonomous consumption c̄, autonomous investment Ī, government expenditure G, and exports X are typically treated as autonomous in this chapter.
An induced variable changes with income — its value is determined inside the model as a function of Y. Examples: induced consumption b·Y, induced saving (1 − b)·Y, and (in richer models) induced taxes t·Y and induced imports m·Y.
The distinction matters because only autonomous variables can be the source of an external "shock" that triggers the multiplier process. Changes in induced variables are responses to changes in income, not initial drivers.
An induced variable changes with income — its value is determined inside the model as a function of Y. Examples: induced consumption b·Y, induced saving (1 − b)·Y, and (in richer models) induced taxes t·Y and induced imports m·Y.
The distinction matters because only autonomous variables can be the source of an external "shock" that triggers the multiplier process. Changes in induced variables are responses to changes in income, not initial drivers.
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Competency-Based Questions — Part 3
Case Study: The economy of Vidyanagar has the consumption function C = 200 + 0.8Y; its potential full-employment income Yf is ₹3,000 cr. Currently autonomous investment Ī = ₹100 cr; the government spends G = ₹100 cr (assumed lump-sum, financed by a head tax that does not feed back into the consumption function for this question).
Q1. The current equilibrium income Y* of Vidyanagar is:
L3 ApplyAnswer: (A) — Total autonomous Ā = c̄ + Ī + Ḡ = 200 + 100 + 100 = 400. k = 1/(1 − 0.8) = 5. Y* = 400 × 5 = ₹2,000 cr.
Q2. Comparing Y* with Yf, the gap in Vidyanagar is:
L4 AnalyseAnswer: (B) — Y* (₹2,000 cr) < Yf (₹3,000 cr) → deflationary gap. The income shortfall is ₹1,000 cr. The autonomous-spending shortfall (vertical distance at Yf) = ΔY ÷ k = 1,000 ÷ 5 = ₹200 cr. AD at Yf = 200 + 0.8 × 3000 + 100 + 100 = 2,800; gap = 3,000 − 2,800 = ₹200 cr — confirmed.
Q3. To reach full employment, the most efficient single policy among the following is:
L5 EvaluateAnswer: (A) — Required ΔY = 1000 cr; with k = 5 we need ΔĀ = 200. (A) ΔG = 200 → ΔY = 5 × 200 = 1,000 ✓ exactly. (B) Tax cut of ₹250 cr raises C by MPC × 250 = 200 → ΔY = 1,000 ✓ — tied. (C) Same as (B): ΔY = 1,000. (D) ΔI = 100 → ΔY = 500 — too small. (A), (B), (C) all reach full employment; (A) does so most directly through G with no leakage to saving in the first round, hence is "most efficient" if the criterion is direct fiscal cost per ΔY. Note: Real-world considerations (tax incidence, multiplier differences) can favour B/C.
HOT Q. Suppose Vidyanagar's MPC suddenly falls from 0.8 to 0.5 because of a sudden panic. Without any policy change, where will the new equilibrium income lie? Will the deflationary gap widen or narrow at Yf? Compute both. What does this episode show about the paradox of thrift?
L6 CreateModel Answer: New k = 1/(1 − 0.5) = 2. Ā unchanged at 400 (assuming the consumption function intercept c̄ stays at 200; the slope falls). New Y* = 400 × 2 = ₹800 cr — far below the original 2,000. The AD line has swung downwards. AD at Yf = 200 + 0.5 × 3,000 + 100 + 100 = ₹1,900 cr; deflationary gap at Yf = 3,000 − 1,900 = ₹1,100 cr — much wider than the earlier ₹200 cr gap. Total savings before the shock: at Y* = 2,000, S = Y − C = 2,000 − (200 + 0.8×2,000) = 2,000 − 1,800 = 200. After the shock at Y* = 800, S = 800 − (200 + 0.5×800) = 800 − 600 = 200. Total saving is unchanged despite a 30 percentage-point rise in MPS — the textbook paradox of thrift in action. The episode also shows why panicked precautionary saving during a downturn is self-defeating: it widens the deflationary gap and deepens the recession.
⚖️ Assertion–Reason Questions — Part 3
Options:
(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.
(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.
Assertion (A): An inflationary gap is removed by contractionary fiscal and monetary policies.
Reason (R): Cutting government expenditure, raising direct taxes, raising the repo rate and raising the cash reserve ratio all reduce aggregate demand.
Answer: (A) — Both A and R are true, and R is the correct explanation of A. An inflationary gap exists because AD > AS at Yf; pulling AD down — fiscally (lower G or higher T) or monetarily (higher repo, CRR, SLR; OMO sales) — closes the gap.
Assertion (A): A deflationary gap is associated with unemployment of factors and a fall in the long-run price level.
Reason (R): When AD < AS at Yf, output settles below full employment; idle factors go unemployed; persistent excess capacity puts downward pressure on prices over time.
Answer: (A) — Both true, and R is the correct explanation. A deflationary gap is the textbook diagnosis of a depression: idle workers, idle machines, and falling prices, all caused by deficient demand at the full-employment level of output.
Assertion (A): To close a deflationary gap of size ΔG = ₹100 cr in an economy with MPC = 0.75, the government needs to raise its expenditure by exactly ₹100 cr.
Reason (R): The gap size is the autonomous-spending shortfall, and the multiplier converts a ΔĀ of ₹100 cr into a ΔY of ₹400 cr.
Answer: (A) — Both true, and R is the correct explanation. The deflationary gap is the vertical distance at Yf — i.e. the autonomous shortfall. With MPC = 0.75, k = 4, so ΔĀ = ₹100 cr produces ΔY = 4 × 100 = ₹400 cr in equilibrium income. Raising G by ₹100 cr restores full employment.
Frequently Asked Questions
What is the inflationary gap in NCERT Class 12 Macroeconomics?
The inflationary gap is the amount by which planned aggregate demand exceeds the aggregate demand needed to maintain full-employment equilibrium. When AD exceeds AS at full employment, the economy cannot raise real output any further, so the excess demand only pushes prices upward, generating inflation. NCERT Class 12 shows the gap on the AD–Y diagram as the vertical distance between the actual AD curve and the AD curve that would intersect AS at the full-employment income level.
What is the deflationary gap in NCERT Class 12 Macroeconomics?
The deflationary gap is the amount by which planned aggregate demand falls short of the aggregate demand needed for full-employment equilibrium. When AD is too small, output and employment fall below their full-employment levels, leaving labour and capacity idle. NCERT Class 12 shows the gap on the AD–Y diagram as the vertical distance between the AD curve that would have produced full employment and the lower AD curve that actually exists. The gap is the source of involuntary unemployment in Keynesian theory.
How can the government correct an inflationary gap?
The government uses contractionary policies to reduce excess aggregate demand. Fiscal policy tools include cutting government expenditure, raising direct taxes (which reduces disposable income and consumption) and reducing transfer payments. Monetary policy tools include the RBI raising the repo rate, raising CRR/SLR and selling government securities through OMO to suck out liquidity. Both sets of measures shift the AD curve downward until it intersects the 45-degree line at the full-employment income level, eliminating the gap.
How can the government correct a deflationary gap?
The government uses expansionary policies to raise aggregate demand. Fiscal policy tools include increasing government expenditure on infrastructure and welfare, cutting direct taxes (which raises disposable income and consumption) and expanding transfer payments. Monetary policy tools include the RBI cutting the repo rate, cutting CRR/SLR and buying government securities through OMO to inject liquidity. Both sets of measures shift the AD curve upward until it intersects the 45-degree line at the full-employment income level, removing the gap.
Why does equilibrium output not always equal full-employment output?
In Keynes's framework, equilibrium output is determined entirely by aggregate demand, not by the supply side. There is no automatic mechanism that adjusts wages or prices fast enough to keep AD high enough for full employment, especially during recessions. So the economy can settle at any level of output below, at, or above full employment. This is the central Keynesian insight in NCERT Class 12: persistent unemployment is possible, and active fiscal and monetary policy is needed to push output to its full-employment level.
What types of questions appear in NCERT Class 12 Chapter 4 exercises?
Chapter 4 exercise questions span definitions (define MPC, multiplier, deflationary gap), short numerical problems (compute equilibrium income given C and I, find the new income after a multiplier shock), diagram-based questions (draw and label the AD–Y diagram with the inflationary gap), and explanation-style questions (why does equilibrium output not always equal full-employment output, list the policy measures for an inflationary gap). Part 3 of this lesson page provides a complete model answer for every Chapter 4 exercise question.
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Class 12 Economics — Introductory Macroeconomics
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