Autonomous investment in an economy rises by Rs 30 crore. When the multiplier process is complete, consumption expenditure has risen by Rs 90 crore in all. What is the marginal propensity to save?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 0.25
The final rise in income is the first rise in investment plus all the rises in consumption it sets off. The multiplier is that total rise ÷ the rise in investment, and it equals 1 ÷ MPS.
Given:
ΔI = Rs 30 crore
Total rise in consumption, ΔC = Rs 90 crore
\( \displaystyle \Delta Y = \Delta I + \Delta C = 30 + 90 = 120 \)
\( \displaystyle k = \frac{\Delta Y}{\Delta I} = \frac{120}{30} = 4 \)
\( \displaystyle MPS = \frac{1}{k} = \frac{1}{4} = 0.25 \)
The MPS is 0.25.
Option (1) 0.33 — this comes from dividing 30 by 90.
Option (3) 0.75 — this is the MPC.
NCERT (2026-27): “4.3.3 The Multiplier Mechanism … The production of final goods employs factors such as labour, capital, land and entrepreneurship. In the absence of indirect taxes or subsidies, the total value of the final goods output is distributed among different factors of production – wages to labour, interest to capital, rent to land etc. Whatever is left over is appropriated by the entrepreneur and is called profit. Thus the sum total of aggregate factor payments in the economy, National Income, is equal to the aggregate value of the output of final goods, GDP. In the above example the value of the extra output, 10, is distributed among various factors as factor payments and hence the income of the economy goes up by 10. When income increases by 10, consumption expenditure goes up by (0.8)10, since people spend 0.8 (= mpc) fraction of their additional income on consumption. Hence, in the next round, aggregate demand in the economy goes up by (0.8)10 and there again emerges an excess demand equal to (0.8)10. Therefore, in the next production cycle, producers increase their planned output further by (0.8)10 to restore equilibrium. When this extra output is distributed among factors, the income of the economy goes up by (0.8)10 and consumption demand increases further by (0.8)210, once again creating excess demand of the same amount. This process goes on, round after round, with producers increasing their output to clear the excess demand in each round and consumers spending a part of their additional income from this extra production on consumption items – thereby creating further excess demand in the next round.” “4.3.3 The Multiplier Mechanism … The increment in equilibrium value of total output thus exceeds the initial increment in autonomous expenditure. 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. Recalling that 10 and 0.8 represent the values of ΔI = ΔA and mpc, respectively, the expression for the multiplier can be explained as”
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