Economic Growth

This chapter analyzes economic growth by examining the aggregate production function. Sources of economic growth are identified and growth rates of different countries are compared.

Growth and the Long-Run Aggregate Supply Curve

Changes in Long-Run Aggregate Supply

The position of the long-run aggregate supply curve is determined by the aggregate production function and the demand and supply curves for labor. A change in any of these will shift the long-run aggregate supply curve.

Figure 8.7 "Shift in the Aggregate Production Function and the Long-Run Aggregate Supply Curve" shows one possible shifter of long-run aggregate supply: a change in the production function. Suppose, for example, that an improvement in technology shifts the aggregate production function in Panel (b) from PF1 to PF2. Other developments that could produce an upward shift in the curve include an increase in the capital stock or in the availability of natural resources.

Figure 8.7 Shift in the Aggregate Production Function and the Long-Run Aggregate Supply Curve

Figure 8.7


An improvement in technology shifts the aggregate production function upward in Panel (b). Because labor is more productive, the demand for labor shifts to the right in Panel (a), and the natural level of employment increases to L2. In Panel (c) the long-run aggregate supply curve shifts to the right to Y2.

The shift in the production function to PF2 means that labor is now more productive than before. This will affect the demand for labor in Panel (a). Before the technological change, firms employed L1 workers at a real wage ω1. If workers are more productive, firms will find it profitable to hire more of them at ω1. The demand curve for labor thus shifts to D2 in Panel (a). The real wage rises to ω2, and the natural level of employment rises to L2. The increase in the real wage reflects labor's enhanced productivity, the amount of output per worker. To see how potential output changes, we see in Panel (b) how much output can be produced given the new natural level of employment and the new aggregate production function. The real GDP that the economy is capable of producing rises from Y1 to Y2. The higher output is a reflection of a higher natural level of employment, along with the fact that labor has become more productive as a result of the technological advance. In Panel (c) the long-run aggregate supply curve shifts to the right to the vertical line at Y2.

This analysis dispels a common misconception about the impact of improvements in technology or increases in the capital stock on employment. Some people believe that technological gains or increases in the stock of capital reduce the demand for labor, reduce employment, and reduce real wages. Certainly the experience of the United States and most other countries belies that notion. Between 1990 and 2007, for example, the U.S. capital stock and the level of technology increased dramatically. During the same period, employment and real wages rose, suggesting that the demand for labor increased by more than the supply of labor. As some firms add capital or incorporate new technologies, some workers at those firms may lose their jobs. But for the economy as a whole, new jobs become available and they generally offer higher wages. The demand for labor rises.

Another event that can shift the long-run aggregate supply curve is an increase in the supply of labor, as shown in Figure 8.8 "Increase in the Supply of Labor and the Long-Run Aggregate Supply Curve". An increased supply of labor could result from immigration, an increase in the population, or increased participation in the labor force by the adult population. Increased participation by women in the labor force, for example, has tended to increase the supply curve for labor during the past several decades.

Figure 8.8 Increase in the Supply of Labor and the Long-Run Aggregate Supply Curve

Figure 8.8


An increase in the supply of labor shifts the supply curve in Panel (a) to S2, and the natural level of employment rises to L2. The real wage falls to ω2. With increased labor, the aggregate production function in Panel (b) shows that the economy is now capable of producing real GDP at Y2. The long-run aggregate supply curve in Panel (c) shifts to LRAS2.

In Panel (a), an increase in the labor supply shifts the supply curve to S2. The increase in the supply of labor does not change the stock of capital or natural resources, nor does it change technology - it therefore does not shift the aggregate production function. Because there is no change in the production function, there is no shift in the demand for labor. The real wage falls from ω1 to ω2 in Panel (a), and the natural level of employment rises from L1 to L2. To see the impact on potential output, Panel (b) shows that employment of L2 can produce real GDP of Y2. The long-run aggregate supply curve in Panel (c) thus shifts to LRAS2. Notice, however, that this shift in the long-run aggregate supply curve to the right is associated with a reduction in the real wage to ω2.

Of course, the aggregate production function and the supply curve of labor can shift together, producing higher real wages at the same time population rises. That has been the experience of most industrialized nations. The increase in real wages in the United States between 1990 and 2007, for example, came during a period in which an increasing population increased the supply of labor. The demand for labor increased by more than the supply, pushing the real wage up. The accompanying Case in Point looks at gains in real wages in the face of technological change, an increase in the stock of capital, and rapid population growth in the United States during the 19th century.

Our model of long-run aggregate supply tells us that in the long run, real GDP, the natural level of employment, and the real wage are determined by the economy's production function and by the demand and supply curves for labor. Unless an event shifts the aggregate production function, the demand curve for labor, or the supply curve for labor, it affects neither the natural level of employment nor potential output. Economic growth occurs only if an event shifts the economy's production function or if there is an increase in the demand for or the supply of labor.