A component of Keynesian theory, MPC represents the proportion of an aggregate raise in pay that is spent on the consumption of goods and services, as opposed to being saved.

|||Let's illustrate this with an example. Suppose you receive a bonus with your paycheck, and it's $500 on top of your normal annual earnings. You suddenly have $500 more in income than you did before. If you decide to spend $400 of this marginal increase in income on a new business suit, your marginal propensity to consume will be 0.8 ($400 divided by $500).