The marginal propensity to consume (MPC) is a measure of how much of an increase in income is typically spent on consumption. It is represented by the symbol c or ΔC/ΔY.
To explain it simply, the MPC tells us the proportion of additional income that is used for consumption rather than saving or other purposes. For example, if the MPC is 0.8, it means that for every additional unit of income, 0.8 units are typically spent on consumption.
The MPC can also be understood as the slope of the consumption function. The consumption function is a mathematical relationship between income and consumption. The MPC represents how much consumption changes for a given change in income.
In the equation C = C + cYd, the coefficient c represents the MPC. This equation shows that consumption (C) is determined by autonomous consumption (C) plus the product of the MPC (c) and disposable income (Yd).
In summary, the MPC is a measure of how much additional income is typically used for consumption. It can be represented as ΔC/ΔY, the slope of the consumption function, or the coefficient c in the consumption equation.