Deficient demand refers to the situation when aggregate demand (AD) is less than the aggregate supply (AS) corresponding to the full employment level of output in the economy.
The situation of deficient demand arises when planned aggregate expenditure falls short of aggregate supply at the full employment level. It gives rise to the deflationary gap. A deflationary gap is a gap by which actual aggregate demand required to establish full employment equilibrium.
The concepts of deficient demand and deflationary gap are shown in Fig. (a)
(i) In the given diagram, income, output and employment are measured on the X-axis and aggregate demand is measured on the Y-axis.
(ii) Aggregate demand (AD) and aggregate supply (AS) curves intersect at point E, which indicates the full-employment equilibrium.
(iii) Due to a decrease in investment expenditure (ΔI), aggregate demand falls from AD to AD1. It denotes the situation of deficient demand and the gap between them, i.e., EG is termed as a deflationary gap.
(iv) Point F indicates the underemployment equilibrium.
Physical measure: Reduction in public expenditure.
Monetary Measure: Increase in money supply.
