Investment and Economic Activity

Read this chapter to examine factors that determine private investment and its link to output within the macroeconomy. Private investment plays an important role in the short run by influencing aggregate demand, and in the long run by influencing the rate of growth of the economy.

14.1 The Role and Nature of Investment


  1. Discuss the components of the investment spending category of GDP and distinguish between gross and net investment.
  2. Discuss the relationship between consumption, saving, and investment, and explain the relationship using the production possibilities model.

How important is investment? Consider any job you have ever performed. Your productivity in that job was largely determined by the investment choices that had been made before you began to work. If you worked as a clerk in a store, the equipment used in collecting money from customers affected your productivity. It may have been a simple cash register, or a sophisticated computer terminal that scanned purchases and was linked to the store's computer, which computed the store's inventory and did an analysis of the store's sales as you entered each sale. If you have worked for a lawn maintenance firm, the kind of equipment you had to work with influenced your productivity. You were more productive if you had the latest mulching power lawn mowers than if you struggled with a push mower. Whatever the work you might have done, the kind and quality of capital you had to work with strongly influenced your productivity. And that capital was available because investment choices had provided it.

Investment adds to the nation's capital stock. We saw in the chapter on economic growth that an increase in capital shifts the aggregate production function outward, increases the demand for labor, and shifts the long-run aggregate supply curve to the right. Investment therefore affects the economy's potential output and thus its standard of living in the long run.

Investment is a component of aggregate demand. Changes in investment shift the aggregate demand curve and thus change real GDP and the price level in the short run. An increase in investment shifts the aggregate demand curve to the right; a reduction shifts it to the left.