Marginal Propensity to Save (MPS)

The marginal propensity to save (MPS) is the fraction of an increase in income that is not spent on an increase in consumption. That is, the marginal propensity to save is the proportion of each additional dollar of household income that is used for saving. It is the slope of the line plotting saving against income.[1] For example, if a household earns one extra dollar, and the marginal propensity to save is 0.35, then of that dollar, the household will spend 65 cents and save 35 cents. Likewise, it is the fractional decrease in saving that results from a decrease in income.

The MPS plays a central role in Keynesian economics as it quantifies the saving-income relation, which is the flip side of the consumption-income relation, and according to Keynes it reflects the fundamental psychological law. The marginal propensity to save is also a key variable in determining the value of the multiplier.

Source: Wikipedia https://en.wikipedia.org/wiki/Marginal_propensity_to_save