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

Investment, Consumption, and Saving

Earlier we used the production possibilities curve to illustrate how choices are made about investment, consumption, and saving. Because such choices are crucial to understanding how investment affects living standards, it will be useful to reexamine them here.

Figure 14.4 "The Choice between Consumption and Investment" shows a production possibilities curve for an economy that can produce two kinds of goods: consumption goods and investment goods. An economy operating at point A on PPC1 is using its factors of production fully and efficiently. It is producing CA units of consumption goods and IA units of investment each period. Suppose that depreciation equals IA, so that the quantity of investment each period is just sufficient to replace depreciated capital; net investment equals zero. If there is no change in the labor force, in natural resources, or in technology, the production possibilities curve will remain fixed at PPC1.

Figure 14.4 The Choice between Consumption and Investment

A society with production possibilities curve PPC1 could choose to produce at point A, producing CA consumption goods and investment of IA. If depreciation equals IA, then net investment is zero, and the production possibilities curve will not shift, assuming no other determinants of the curve change. By cutting its production of consumption goods and increasing investment to IB, however, the society can, over time, shift its production possibilities curve out to PPC2, making it possible to enjoy greater production of consumption goods in the future.

Now suppose decision makers in this economy decide to sacrifice the production of some consumption goods in favor of greater investment. The economy moves to point B on PPC1. Production of consumption goods falls to CB, and investment rises to IB. Assuming depreciation remains IA, net investment is now positive. As the nation's capital stock increases, the production possibilities curve shifts outward to PPC2. Once that shift occurs, it will be possible to select a point such as D on the new production possibilities curve. At this point, consumption equals CD, and investment equals ID. By sacrificing consumption early on, the society is able to increase both its consumption and investment in the future. That early reduction in consumption requires an increase in saving.

We see that a movement along the production possibilities curve in the direction of the production of more investment goods and fewer consumption goods allows the production of more of both types of goods in the future.