## Consumption and the Aggregate Expenditures Model

Read this chapter to examine consumption and its determinants within the aggregate expenditures model. Consumption is the largest component of Aggregate Demand the United States, therefore, the factors that determine consumption, also determine the success of the economy.

### 13.3 Aggregate Expenditures and Aggregate Demand

#### The Multiplier and Changes in Aggregate Demand

In the aggregate expenditures model, a change in autonomous aggregate expenditures changes equilibrium real GDP by the multiplier times the change in autonomous aggregate expenditures. That model, however, assumes a constant price level. How can we incorporate the concept of the multiplier into the model of aggregate demand and aggregate supply?

Consider the aggregate expenditures curves given in Panel (a) of Figure 13.14 "Changes in Aggregate Demand", each of which corresponds to a particular price level. Suppose net exports rise by $1,000 billion. Such a change increases aggregate expenditures at each price level by $1,000 billion.

A $1,000-billion increase in net exports shifts each of the aggregate expenditures curves up by $1,000 billion, to *AE*′_{P=1.0} and *AE*′_{P=1.5}. That changes the equilibrium real GDP associated with each price level; it
thus shifts the aggregate demand curve to *AD*_{2} in Panel (b). In the aggregate expenditures model, equilibrium real GDP changes by an amount equal to the initial change in autonomous aggregate expenditures times the multiplier, so
the aggregate demand curve shifts by the same amount. In this example, we assume the multiplier is 2. The aggregate demand curve thus shifts to the right by $2,000 billion, two times the $1,000-billion change in autonomous aggregate expenditures.

**Figure 13.14** Changes in Aggregate Demand

*The aggregate expenditures curves for price levels of 1.0 and 1.5 are the same as in Figure 13.13 "From Aggregate Expenditures to Aggregate Demand", as is the aggregate demand curve. Now suppose a $1,000-billion increase in net exports shifts each of the aggregate expenditures curves up; AE_{P=1.0},
for example, rises to AE′_{P=1.0}. The aggregate demand curve thus shifts to the right by $2,000 billion, the change in aggregate expenditures times the multiplier, assumed to be 2 in this example.*

In general, any change in autonomous aggregate expenditures shifts the aggregate demand curve. The amount of the shift is always equal to the change in autonomous aggregate expenditures times the multiplier. An increase in autonomous aggregate expenditures shifts the aggregate demand curve to the right; a reduction shifts it to the left.