Determination of Income and Employment

🧠 First Principles — Read This First

Plans and outcomes are different numbers. A producer who plans to add Rs 100 to her stocks but has to sell Rs 30 of them ends the year with Rs 70 of inventory investment. NCERT calls the planned value ex ante and the realised value ex post. The national accounts of chapter 2 record ex post values, and those always balance. This chapter is about ex ante values, which balance only in equilibrium.

With prices fixed, demand sets output. NCERT assumes idle machines and workers, so firms can produce more without raising costs or prices. Output then settles where planned output equals planned demand: Y = C̄ + Ī + cY, which gives Y = (C̄ + Ī) ÷ (1 − c). If demand falls short, unsold goods pile up and firms cut output; if demand runs ahead, stocks run down and firms raise it. NCERT calls this the effective demand principle.

Spending feeds on itself. Ten more units of investment become ten units of income; people spend the fraction c of it, which becomes someone else's income, and so on. With c = 0.8 the rounds add up to 10 ÷ (1 − 0.8) = 50: the multiplier is 5. The same arithmetic runs backwards. If everyone tries to save more, income falls until saving is no higher than before (the paradox of thrift), and the equilibrium reached need not employ everyone.

PART 1 — Quick Reference

The Chapter at a Glance

Demand in India's Economy, Dated (record, not NCERT)

NCERT's model has consumption (C), investment (I) and, briefly, government spending (G). Their sizes in India's accounts, and the part of autonomous spending that the Union Government sets in its Budget, are below. Each figure is from the issuing body's own document.

Read the capital-expenditure rows by their basis. A budget estimate is a plan, a revised estimate is the year's second look, and only an actual is a result: the 2025-26 budget estimate (₹11.21 lakh crore) was revised down to ₹10.96 lakh crore, and the 2022-23 estimate of ₹7.50 lakh crore ended at ₹7.40 lakh crore.

PART 2 — Concepts & Narrative

Opening: Models and "Other Things Remaining Equal"

The aim of macroeconomics is to build models that explain "what causes periods of slow growth or recessions in the economy, or increment in the price level, or a rise in unemployment". All the variables cannot be handled at once, so the model holds the others constant while solving for one. NCERT calls this the assumption of ceteris paribus, "which literally means 'other things remaining equal'". This chapter determines national income "under the assumption of fixed price of final goods and constant rate of interest", and "the theoretical model used in this chapter is based on the theory given by John Maynard Keynes". For Keynes, the General Theory (1936) and the Great Depression that prompted it, see Introduction.

4.1 Aggregate Demand and Its Components

NCERT's example. A producer plans to add Rs 100 worth of goods to her stock during the year, so her planned investment is Rs 100. Demand turns out higher than expected, and she sells Rs 30 of goods from her stock. Her inventory rises by only Rs 100 − 30 = Rs 70. Planned (ex ante) investment is Rs 100; actual (ex post) investment is Rs 70. "In simple words, ex-ante depicts what has been planned, and ex-post depicts what has actually happened." Income determination needs the planned values of the components of aggregate demand.

4.1.1 Consumption

"The most important determinant of consumption demand is household income." The simplest consumption function assumes consumption changes at a constant rate as income changes:

C = C̄ + cY (eq. 4.1)

• C̄, autonomous consumption: consumption that does not depend on income. Even at zero income some consumption takes place.
• cY, induced consumption: the part that depends on income. When income rises by Re 1, induced consumption rises by c.
• c, the marginal propensity to consume (MPC): MPC = ΔC ÷ ΔY = c.

ΔC cannot exceed ΔY, so c cannot exceed 1; a consumer may also leave consumption unchanged when income changes, so c can be 0. "Generally, MPC lies between 0 and 1 (inclusive of both values)."

Imagenia. NCERT's imaginary country has C = 100 + 0.8Y. "Even when Imagenia does not have any income, its citizens still consume Rs. 100 worth of goods": autonomous consumption is 100. Its MPC is 0.8, so if income rises by Rs 100, consumption rises by Rs 80.

Saving. "Savings is that part of income that is not consumed": S = Y − C. The marginal propensity to save is MPS = ΔS ÷ ΔY = s. Since ΔS = ΔY − ΔC, s = 1 − c. Substituting the consumption function gives the saving function S = −C̄ + (1 − c)Y: at zero income, saving is −C̄ (people consume by running down past savings).

NCERT's definitions box:

Two results follow from the definitions. APC = C̄ ÷ Y + c, so with C̄ > 0 the APC is always above the MPC and falls as income rises. And APC + APS = 1, just as MPC + MPS = 1. Imagenia's consumption equals its income where Y = 100 + 0.8Y, at Y = 500 (APC = 1, saving zero). Below that income it dissaves: at Y = 250, C = 300 and S = −50.

4.1.2 Investment

Investment is "addition to the stock of physical capital (such as machines, buildings, roads etc., i.e. anything that adds to the future productive capacity of the economy) and changes in the inventory (or the stock of finished goods) of a producer". Machines are final goods, not intermediate goods: they are not used up in a year but yield services over many years.

"Investment decisions by producers, such as whether to buy a new machine, depend, to a large extent, on the market rate of interest." For simplicity NCERT assumes firms plan to invest the same amount every year:

I = Ī (eq. 4.2), where Ī is autonomous (given, or exogenous) investment.

4.2 Determination of Income in Two-Sector Model

In an economy without a government, ex ante aggregate demand for final goods is planned consumption plus planned investment:

AD = C̄ + Ī + cY

If the final goods market is in equilibrium, planned output Y equals this demand:

Y = Ā + cY (eq. 4.3), where Ā = C̄ + Ī is total autonomous expenditure.

Equilibrium condition, not accounting identity. The Y on the left of eq. 4.3 is planned supply; the right side is planned demand. They are equal only in equilibrium. The accounting identity of chapter 2 (actual output equals actual consumption plus actual investment) holds always. If planned demand falls short of planned output, eq. 4.3 does not hold: "Stocks will be piling up in the warehouses which we may consider as unintended accumulation of inventories". Actual output still equals actual C + I, because the unsold goods are counted in actual investment.

Two kinds of inventory investment. Inventory investment can be positive (stocks rise) or negative (stocks fall). It is planned when the firm decides to keep stocks, and unplanned when sales differ from what the firm expected, so it has to add to or run down its stocks. In NCERT's opening example, planned inventory investment is +100 and unplanned is −30.

The government, briefly. Government spending G adds to demand; taxes T reduce household disposable income to Y − T. The equation becomes Y = C̄ + Ī + G + c(Y − T). The term G − cT simply adds to autonomous expenditure, which "does not significantly change the analysis in any qualitative way", so NCERT sets the government aside for the rest of the chapter. Without indirect taxes and subsidies, it treats GDP and national income as the same thing and uses Y for both.

NCERT returns to the government in chapter 5, where it derives the multipliers for government spending, taxes and a balanced budget (Government Budget and the Economy), and to foreign trade in chapter 6, where imports reduce the multiplier (Open Economy Macroeconomics).

4.3 Determination of Equilibrium Income in the Short Run

Macroeconomic theory proceeds in two steps: first an equilibrium with the price level fixed, then one in which it varies. NCERT gives two reasons for fixing the price level at the first step:

1. The economy has unused resources (machinery, buildings, labour). "In such a situation, the law of diminishing returns will not apply; hence additional output can be produced without increasing marginal cost." So the price level does not change when output changes.
2. "This is just a simplifying assumption which will be changed later."

4.3.1 Macroeconomic Equilibrium with Price Level Fixed

(A) Graphical method.

1. A straight line in intercept form (Fig. 4.1): Y = a + bX has intercept a on the vertical axis and slope b (= tan θ).
2. Consumption function (Fig. 4.2): C = C̄ + cY is a line with intercept C̄ and slope c (= tan α).
3. Investment function (Fig. 4.3): I = Ī is a horizontal line at height Ī, the same at every income.
4. Aggregate demand (Fig. 4.4): add the consumption and investment lines vertically. With OM = C̄ and OJ = Ī, the AD line starts at OL = C̄ + Ī and is parallel to the consumption line (same slope c). It shows ex ante demand.
5. Aggregate supply (Fig. 4.5): with prices fixed and resources idle, "Whatever is the level of GDP, that much will be supplied and price level has no role to play." Supply is the 45° line, on which "every point on it has the same horizontal and vertical coordinates". NCERT's example: at a GDP of Rs 1,000 (point A on the horizontal axis) Rs 1,000 worth of goods is supplied, shown at B on the 45° line.
6. Equilibrium (Fig. 4.6): where the AD line cuts the 45° line, at E, ex ante demand equals ex ante supply; equilibrium income is OY₁.

(B) Algebraic method. Set ex ante aggregate demand equal to ex ante aggregate supply:

C̄ + Ī + cY = Y, so Y(1 − c) = C̄ + Ī, and Y = (C̄ + Ī) ÷ (1 − c) (eq. 4.4)

NCERT's worked example. Let C = 40 + 0.8Y and I = 10. Then Y = 40 + 0.8Y + 10, so Y = 50 + 0.8Y, and Y = 50 ÷ (1 − 0.8) = 250.

Check it, and see what happens away from it (worked from NCERT's numbers):

4.3.2 Effect of an Autonomous Change in Aggregate Demand on Income and Output

Equilibrium income depends on aggregate demand, so a change in demand changes it. Demand can change through:

1. Consumption: a change in autonomous consumption C̄, or in the MPC c.
2. Investment: investment does not depend on income, but other things move it. "Easy availability of credit encourages investment", and since the interest rate is the cost of investible funds, "at higher interest rates, firms tend to lower investment".

NCERT's example continued. Investment rises from 10 to 20. Autonomous expenditure becomes 60, and the new equilibrium is Y = 60 ÷ 0.2 = 300. The AD line shifts up in parallel from AD₁ (50 + 0.8Y) to AD₂ (60 + 0.8Y). At the old output of 250, demand is now 260: excess demand of 10, the distance E₁F in Fig. 4.7, equal to the rise in investment. The new equilibrium is where AD₂ cuts the 45° line, at E₂. Output has risen by 50, five times the rise in investment of 10. Section 4.3.3 explains why.

4.3.3 The Multiplier Mechanism

Producing final goods employs labour, capital, land and entrepreneurship. With no indirect taxes or subsidies, the value of the output is paid out as wages, interest, rent and profit, so the extra output of 10 raises the economy's income by 10. People spend 0.8 of the extra income, so demand rises by (0.8)10 = 8 in the next round, producers raise output by 8 to meet it, incomes rise by 8, consumption by (0.8)²10 = 6.4, and so on. Each round, producers clear the excess demand, and consumers spend part of the new income, creating smaller excess demand in the next round.

Table 4.1, with NCERT's numbers:

The total is the sum of an infinite geometric series:

10 + (0.8)10 + (0.8)²10 + … = 10 × {1 + 0.8 + (0.8)² + …} = 10 ÷ (1 − 0.8) = 50

Of the extra income of 50, households spend 40 (0.8 × 50) and save 10 (0.2 × 50): the new saving exactly matches the new investment of 10.

"The ratio of the total increment in equilibrium value of final goods output to the initial increment in autonomous expenditure is called the investment multiplier of the economy":

Investment multiplier = ΔY ÷ ΔĀ = 1 ÷ (1 − c) = 1 ÷ s (eq. 4.5)

"As c becomes larger the multiplier increases." With an autonomous increase of 10:

The multiplier works both ways: a fall of 10 in autonomous spending lowers equilibrium income by 50 when c = 0.8.

Paradox of Thrift

NCERT's example. Start at Y = 250 (C = 40 + 0.8Y, I = 10). People suddenly become thrifty, perhaps after "new information regarding an imminent war or some other impending disaster", and the MPC falls from 0.8 to 0.5.

1. At the old income of 250, consumption and demand fall by (0.8 − 0.5) × 250 = 75. Output now exceeds demand by 75; stocks pile up.
2. Producers cut output by 75; incomes fall by 75; consumption falls by (0.5)75 = 37.5; output is cut again, and so on: 75 + 37.5 + 18.75 + …
3. Total fall in output = 75 ÷ (1 − 0.5) = 150, so the new equilibrium is Y = 100. Directly: Y = 50 ÷ (1 − 0.5) = 100.
4. Saving before: 250 − (40 + 0.8 × 250) = 10. Saving after: 100 − (40 + 0.5 × 100) = 10. Total saving has not risen at all, and income has fallen by 150.

Why exactly 10? In this model investment is fixed at Ī = 10, and in equilibrium planned saving must equal planned investment, so saving ends at 10 whatever the MPC. If investment instead rose and fell with income, the fall in income would cut investment, and saving would end lower than before: NCERT's "decline".

Parametric shift. "When Ā changes the line shifts upwards or downwards in parallel. When c changes, however, the line swings up or down." A rise in the MPS (fall in the MPC) lowers the slope of the AD line, which swings downwards about its intercept Ā (Fig. 4.8).

4.4 Some More Concepts

Equilibrium output also sets the level of employment, given the other factors of production. But the output at which Y equals AD "does not necessarily mean the level of output at which everyone is employed".

• Full employment: "Full employment level of income is that level of income where all the factors of production are fully employed in the production process."
• Equilibrium is not full employment: "Equilibrium only means that if left to itself the level of income in the economy will not change even when there is unemployment in the economy."
• Deficient demand: equilibrium output below full-employment output, because demand is not enough to employ all factors. "This situation is called the situation of deficient demand. It leads to decline in prices in the long run."
• Excess demand: equilibrium output above full-employment output, because demand exceeds what the economy produces at full employment. "This situation is called the situation of excess demand. It leads to rise in prices in the long run."

An illustration with NCERT's numbers (the full-employment output of 300 is assumed for the example). With I = 10, equilibrium income is 250, below 300: deficient demand. At full-employment output, planned demand is 50 + 0.8 × 300 = 290, short of output by 10. A rise in autonomous spending of 10, as in section 4.3.2, raises income by 5 × 10 = 50 and closes it. If investment were 30 instead, equilibrium income would be 70 ÷ 0.2 = 350, above 300: excess demand, with planned demand at full employment of 310 against output of 300.

NCERT's Summary: The Effective Demand Principle

When, at a particular price level, aggregate demand for final goods equals aggregate supply, the product market is in equilibrium. Aggregate demand is made of ex ante consumption, ex ante investment, government spending and so on. NCERT assumes a constant final-goods price and a constant interest rate in the short run. "We also assume that the aggregate supply is perfectly elastic at this price. Under such circumstances, aggregate output is determined solely by the level of aggregate demand. This is known as effective demand principle." An increase (decrease) in autonomous spending raises (lowers) output by a larger amount through the multiplier.

PART 3 — UPSC Integration

Three Frameworks

1. Plans versus the record. The accounting identity (actual output = actual C + actual I) holds every year; the equilibrium condition (planned output = planned C + planned I) holds only at equilibrium. The gap between them is unplanned inventory investment. Any question on "ex ante and ex post" or "unintended inventories" is a question about this gap.

2. Shift or swing. A change in autonomous spending (C̄, Ī, or G in chapter 5) shifts the AD line in parallel and moves income by multiplier × change. A change in the MPC swings the line and changes the multiplier itself. Name which parameter moved before computing anything.

3. Model to record. In NCERT's model Ā is autonomous spending; in India's accounts consumption is about 57 per cent of GDP and fixed investment about 32 per cent (2025-26), and Union capital expenditure is the slice the Budget sets directly. The Union Budget 2022-23 put the logic in one line: "the virtuous cycle of investment requires public investment to crowd-in private investment" (para 100). When you use budget figures, say whether each is an estimate or an actual.

Confused Pairs

Exam Strategy

• Prelims: NCERT's numbers are the questions: Rs 100 planned and Rs 70 actual inventory investment; Imagenia (C = 100 + 0.8Y); 50 ÷ 0.2 = 250 and 60 ÷ 0.2 = 300; the rounds 10, 8, 6.4 summing to 50; the paradox of thrift (75 at the first round, 150 in all, 250 to 100, saving 10 both times). Know which way the AD line moves for a change in Ā (parallel) and in c (swing), and that deficient demand lowers prices only in the long run.
• Mains (GS3): for questions on public capital expenditure, slowdowns or demand stimulus, start with the effective demand principle and the multiplier, then give the leakages that make the real multiplier smaller (saving, taxes, imports: NCERT chapters 5 and 6), then the dated record (consumption and investment shares from NAS 2026; capital expenditure as estimate and as actual). Use "deficient demand" and "excess demand" as NCERT defines them, and say which gap you mean.
• Numericals: equilibrium Y = Ā ÷ (1 − c); ΔY = ΔĀ ÷ (1 − c); for a fall in the MPC, compute the new equilibrium directly with the new c. Check every answer by putting it back into AD.

Practice Questions

Prelims (UPSC-pattern, not past papers)

1. A producer plans to add Rs 100 of goods to her stock during a year. Because sales are higher than she expected, she has to sell Rs 30 of goods from her stock. Her ex ante and ex post investment are: (a) Rs 100 and Rs 70 (b) Rs 70 and Rs 100 (c) Rs 100 and Rs 130 (d) Rs 30 and Rs 70 Answer: (a). Planned is Rs 100; stocks actually rise by 100 − 30 = Rs 70 (NCERT p. 2).

2. In Imagenia, C = 100 + 0.8Y. Consider the following statements for an income of 1,000:

   1. The average propensity to consume is 0.9.
   2. The marginal propensity to save is 0.2.
   3. Saving is 200.

   Which of the statements given above are correct? (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: (a). C = 900, so APC = 0.9 and saving = 100; MPS = 1 − 0.8 = 0.2.

3. In a two-sector economy, C = 40 + 0.8Y and autonomous investment is 10. If investment rises to 20, equilibrium income changes from: (a) 250 to 260 (b) 250 to 300 (c) 50 to 60 (d) 200 to 250 Answer: (b). 50 ÷ 0.2 = 250 and 60 ÷ 0.2 = 300; the multiplier is 5 (NCERT pp. 8-10).

4. Consider the following statements about the investment multiplier in NCERT's model:

   1. It equals 1 ÷ (1 − MPC), which is the same as 1 ÷ MPS.
   2. It becomes smaller as the MPC rises.
   3. If the MPC is zero, the multiplier is 1.

   Which of the statements given above are correct? (a) 1 and 3 only (b) 1 and 2 only (c) 2 and 3 only (d) 1, 2 and 3 Answer: (a). "As c becomes larger the multiplier increases."

5. In NCERT's example, autonomous expenditure is 50 and the MPC falls from 0.8 to 0.5. Which one of the following follows? (a) Income falls from 250 to 100 and total saving stays at 10 (b) Income falls from 250 to 175 and total saving rises (c) Income is unchanged and total saving rises (d) Income falls from 250 to 100 and total saving falls to zero Answer: (a). The first-round fall of 75 grows to 150 through the multiplier of 2; saving is 10 at both equilibria (paradox of thrift). Option (b) stops at the first round.

6. Consider the following statements about the aggregate demand line AD = Ā + cY:

   1. A rise in autonomous consumption shifts the line upwards, parallel to itself.
   2. A fall in the marginal propensity to consume makes the line swing downwards.
   3. A rise in autonomous investment makes the line steeper.

   Which of the statements given above are correct? (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: (a). Investment is part of the intercept Ā; only c changes the slope.

7. Consider the following statements based on NCERT:

   1. Equilibrium income is always the full-employment level of income.
   2. Deficient demand leads to a decline in prices in the long run.
   3. Excess demand arises when equilibrium output is more than the full-employment level of output.

   Which of the statements given above are correct? (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 Answer: (b). Equilibrium can sit below full employment: it only means income will not change if left to itself.

8. In a closed economy the MPC is 0.8 and the government levies a proportional income tax at 25 per cent. The autonomous expenditure multiplier is: (a) 2.22 (b) 2.5 (c) 4 (d) 5 Answer: (b). 1 ÷ [1 − c(1 − t)] = 1 ÷ (1 − 0.6) = 2.5 (NCERT ch 5, eq. 5.18). Option (a) comes from the wrong formula 1 ÷ (MPS + t); 5 is the multiplier without the tax.

NCERT Exercises 1-6 (worked answers)

1. MPC and its relation to MPS. The MPC is the change in consumption per unit change in income, c = ΔC ÷ ΔY; NCERT allows it to lie between 0 and 1, both included. The MPS is the change in saving per unit change in income, s = ΔS ÷ ΔY. Every extra rupee of income is either consumed or saved, so ΔC + ΔS = ΔY and MPC + MPS = 1, or s = 1 − c. In Imagenia (C = 100 + 0.8Y), MPC = 0.8 and MPS = 0.2.
2. Ex ante versus ex post investment. Ex ante investment is what producers plan to invest; ex post investment is what they actually end up investing, as recorded in the accounts. They differ by unplanned inventory investment. NCERT's producer plans Rs 100 but, after selling Rs 30 from stock, invests Rs 70. Ex post, output always equals C + I; ex ante, the two are equal only in equilibrium.
3. Parametric shift of a line. A line shifts when one of its parameters (intercept or slope) changes, not when a variable moves along it. (i) If the slope decreases, the line swings downwards about its intercept and becomes flatter: the AD line 50 + 0.8Y becomes 50 + 0.5Y when the MPC falls. (ii) If the intercept increases, the line shifts upwards parallel to itself: 50 + 0.8Y becomes 60 + 0.8Y when investment rises by 10.
4. Effective demand and the multiplier. With the price of final goods and the rate of interest given, and aggregate supply perfectly elastic, output is determined solely by aggregate demand: the effective demand principle. Equilibrium requires Y = Ā + cY, so Y = Ā ÷ (1 − c). A change ΔĀ changes equilibrium income by ΔY = ΔĀ ÷ (1 − c), so the autonomous expenditure multiplier is ΔY ÷ ΔĀ = 1 ÷ (1 − c). The same result comes from the rounds: ΔĀ(1 + c + c² + …) = ΔĀ ÷ (1 − c).
5. Ā = Rs 50 crore, MPS = 0.2, Y = Rs 4,000 crore. MPC = 1 − 0.2 = 0.8. Ex ante aggregate demand = Ā + cY = 50 + 0.8 × 4,000 = Rs 3,250 crore. Output (Rs 4,000 crore) exceeds planned demand by Rs 750 crore, so the economy is not in equilibrium: there is excess supply, unsold goods of Rs 750 crore pile up as unintended inventories, and producers will cut output. Equilibrium income is Ā ÷ (1 − c) = 50 ÷ 0.2 = Rs 250 crore.
6. Paradox of thrift. If everyone saves a larger proportion of income, total saving does not rise; it falls or stays the same. Higher saving means lower consumption, so demand falls short of output, firms cut production and incomes fall through the multiplier until saving again equals investment. In NCERT's example the MPC falls from 0.8 to 0.5, income falls from 250 to 100, and saving is 10 before and after. What is prudent for one household cuts the incomes of all when everyone does it at once.

📦 Revision Capsule

Sources

• NCERT, Introductory Macroeconomics (Class XII), ch. 4 "Determination of Income and Employment", Reprint 2026-27: ncert.nic.in PDF; ch. 5 "Government Budget and the Economy" (eq. 5.18): ncert.nic.in PDF; ch. 6 "Open Economy Macroeconomics" (eq. 6.8): ncert.nic.in PDF.
• J. M. Keynes, The General Theory of Employment, Interest and Money (Macmillan, 1936), ch. 12, section VII, p. 161: archive.org scan.
• MoSPI (National Statistics Office), National Accounts Statistics 2026, released 31 August 2026: publication page; Statement 8.17.1, provisional estimates of national income and other macroeconomic aggregates, 2025-26: xlsx.
• Ministry of Finance, Budget at a Glance 2026-27, Union Budget of February 2026 (paras 4-5): indiabudget.gov.in PDF.
• Ministry of Finance, Statements of Fiscal Policy as required under the Fiscal Responsibility and Budget Management Act, 2003, February 2026 (paras 22-24): indiabudget.gov.in PDF.
• Ministry of Finance, Budget at a Glance 2024-25 (Effective Capital Expenditure of Government, Actuals 2022-23): indiabudget.gov.in PDF.
• Ministry of Finance, Budget Speech 2022-23, 1 February 2022 (paras 100-101): indiabudget.gov.in PDF.
• PIB, Highlights of the Union Budget 2025-26, 1 February 2025: static.pib.gov.in PDF.