Effective demand refers to the willingness and ability of consumers to purchase goods at different prices. It shows the amount of goods that consumers are actually buying – supported by their ability to pay.
In Keynes’s macroeconomic theory, effective demand is the point of equilibrium where aggregate demand = aggregate supply. The importance of Keynes’ view is that effective demand may be insufficient to achieve full employment due to unemployment and workers without income to produce unsold goods.
The two determinants of effective demand are consumption and investment expenditures. When income increases consumption expenditure also increases but by less than the increase in income. Thus there arises a gap between income and consumption which leads to decline in the volume of employment.