# AP Macroeconomics : How to find national saving

## Example Questions

### Example Question #1 : How To Find National Saving

If the income level in a given economy increases by $100 and spending increases by$80, the marginal propensity to save in that economy is equal to which of the following?

0.2

0.75

0.5

0.8

0.2

Explanation:

The marginal propensity to consume is calcuated by the change in consumption over the change in income. In this example, the marginal propensity to consume is 80/100 = 0.8. However, the problem asks for the marginal propensity to save and not the marginal propensity to consume.

In any economy, whatever money is not used for consumption is considered savings. Therefore, to find the marginal propensity to save, subtract the marginal propensity to consume from 1. Thus, 1 - 0.8 = 0.2. The marginal propensity to consume in this problem would be 0.2.