614 PA R T V I I Monetary Theory Interest Rate, i LM(P3) LM(P2) Price Level, P LM(P1) i3 P3 i2 P2 i1 P1 AD IS Y3 Y2 Y1 Y3 Y1 (b) Aggregate demand curve (a) ISLM diagram F I G U R E - 11 Y2 Aggregate Output, Y Aggregate Output, Y Deriving the Aggregate Demand Curve The ISLM diagram in panel (a) shows that as the price level rises from P1 to P2 to P3, the LM curve shifts to the left, and equilibrium output falls The combinations of the price level and equilibrium output from panel (a) are then plotted in panel (b), and the line connecting them is the aggregate demand curve AD IS curve is at point 1, where output is Y1 The equilibrium output level Y1 that occurs when the price level is P1 is also plotted in panel (b) as point If the price level rises to P2, then in real terms the money supply has fallen The effect on the LM curves is identical to a decline in the nominal money supply when the price level is fixed The LM curve will shift leftward to LM (P2) The new equilibrium level of output has fallen to Y2 because planned investment and net exports fall when the interest rate rises Point in panel (b) plots this level of output for price level P2 A further increase in the price level to P3 causes a further decline in the real money supply, leading to a further decline in planned investment and net exports, and output declines to Y3 Point in panel (b) plots this level of output for price level P3 The line that connects the three points in panel (b) is the aggregate demand curve AD, and it indicates the level of aggregate output consistent with equilibrium in the goods market and the market for money at any given price level This aggregate demand curve has the usual downward slope because a higher price level reduces the money supply in real terms, raises interest rates, and lowers the equilibrium level of aggregate output Factors That Cause the Aggregate Demand Curve to Shift ISLM analysis demonstrates how the equilibrium level of aggregate output changes for a given price level A change in any factor (except a change in the price level) that causes the IS or LM curve to shift causes the aggregate demand curve to shift To see how this works, let s first look at what happens to the aggregate demand curve when the IS curve shifts Five factors cause the IS curve to shift: changes in autonomous consumer spending, changes in investment spending related to business confidence, changes in government spending, changes in taxes, and autonomous changes in net exports How changes in these factors lead to a shift in the aggregate demand curve is examined in Figure 23-12 SHIFTS IN THE IS CURVE