The document discusses the concepts of equilibrium income, excess demand, deficient demand, and the multiplier effect in Keynesian economics. It provides definitions and diagrams to illustrate:
1) Equilibrium income is determined by the point where aggregate demand (AD) equals aggregate supply (AS). The economy can be at full employment, under-employment, or over-employment.
2) Excess demand occurs when AD is greater than AS at full employment, leading to inflation. Deficient demand is when AD is less than AS, resulting in under-employment.
3) The investment multiplier shows how a initial change in investment causes a multiplied change in equilibrium income through subsequent rounds of spending. A higher multiplier coefficient corresponds to