1. Keynesian Economics
According to John Maynard Keynes: in the short-run, the level of GDP is determined primarily by demand.

2. Keynesian Consumption Function
The relationship between consumer spending and income, in the short-run, has two parts: C = Ca + by
C = Consumption Spending;
Ca = Autonomous Consumption Spending;
b = Marginal Propensity to Consume; and
y = Level of Income.

3. Keynesian Saving Function
The relationship between the level of saving and the level of income, in the short-run, is:
S = - Ca + (1 - b)y
S = Consumer Saving;
Ca = Autonomous Consumption Spending;
1 - b = Marginal Propensity to Save; and
y = Level of Income.