Consumption function

In economics, the consumption function shows a relationship between consumption and disposable income. It is believed that John Maynard Keynes introduced the idea in macroeconomics in 1936. He used it to develop the idea of a government spending multiplier. 
Details.
Its simplest form is the "linear consumption function". It is used often in simple Keynesian models:
where formula_2 is the autonomous consumption that is independent of disposable income; in other words, consumption when there is no income. The term formula_3 is the induced consumption that is influenced by the economy's income level. It is generally assumed that there is no correlation or dependence between formula_4 and "C".