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Comprehension:

Read the passage carefully and answer the questions based on the passage:

Aggregate Demand and Its Components

Consumption may denote not what people have actually consumed in a given year, but what they had planned to consume during the same period. Similarly, investment can mean the amount a producer plans to add to her inventory. It may be different from what she ends up doing. The planned values of the variables are called their ex ante measures. The most important determinant of consumption demand is household income. A consumption function describes the relation between consumption and income. The simplest consumption function assumes that consumption changes at a constant rate as income changes. Of course, even if income is zero, some consumption still takes place. Since this level of consumption is independent of income, it is called autonomous consumption. The induced component of consumption, cY shows the dependence of consumption on income.

Savings are that part of income that is not consumed. What is the marginal propensity to save?

Solution

✅ Correct Option: 4

Option 1 -> S/Y represents the average propensity to save, not the marginal propensity to save.

Option 2 -> C/Y represents the average propensity to consume, not related to marginal propensity to save.

Option 3 -> ΔS is simply the change in savings, not a propensity ratio.

Option 4 -> 1-c correctly represents the marginal propensity to save, where c is the marginal propensity to consume.


Hence, 1-c -> The marginal propensity to save (MPS) is the proportion of additional income that is saved rather than consumed. Since income can only be either consumed or saved (Y = C + S), the marginal propensities must sum to 1. Therefore, MPS = 1 - MPC = 1 - c, where c represents the marginal propensity to consume. For example, if MPC = 0.8 (80% of additional income is consumed), then MPS = 0.2 (20% is saved) -> correct

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