To find the minimum change in investment spending necessary to achieve a specified increase in GDP, we must understand the role of the ________, which indicates the proportion of additional income that is saved rather than spent.

To find the minimum change in investment spending needed to achieve a certain increase in GDP, we need to understand the concept of the marginal propensity to save (MPS). The MPS shows how much of each additional dollar of income is saved instead of spent. For example, if the MPS is 0. 2, it means that for every extra dollar earned, 20 cents is saved and 80 cents is spent. This understanding helps us calculate how much more investment is needed to boost GDP because we can see how much of the new income will actually be spent in the economy.