What is Marginal Propensity to consume? How is it related to Marginal Propensity to Save?

Answer:

The marginal propensity to consume is the ratio of change in consumption expenditure to a change income.

Marginal Propensity to consume = Change in Consumption / Change in Income

MPC = ∆C / ∆Y

The marginal propensity to save is the ratio of change in saving to a change income.

Marginal Propensity to save = Change in saving / Change in Income

MPS = ∆S / ∆Y

Aggregate of marginal propensity to consume and marginal propensity to save is equal to one

MPC + MPS = 1

Also read : 

Consumption function

Saving function

Relationship between Investment multiplier and Marginal propensity to consume

There is a direct relationship between multiplier and MPC. Higher the value of MPC, higher the multiplier affect and lower is the value of multiplier, lower the multiplier effect. 

We have already derived the multiplier formula i.e 

K = 1 / 1-MPC

Now we see the multiplier effect by taking different values of MPC

If MPC = 0.5 

K = 1 / 1-MPC

K = 1 / 1-0.5

    = 1 / 0.5

    = 2