The relationship between consumption and income is called the consumption function Symbolically,
C = f (Y)
In equation,
C = C + bY
C > 0 ; 0 < b < 1
Where, C = consumption
C = autonomous consumption at zero level of income.
b = MPC
Y = level of income.
As the consumption function shows, there is a positive relationship between income and consumption. The slope of the curve is MPC, which is equal to ∆C/∆Y.