11.3Shifts in Aggregate Supply

For example, the vertical and horizontal axes have distinctly different meanings in macroeconomic and microeconomic diagrams. The vertical axis of a microeconomic demand and supply diagram expresses a price (or wage or rate of return) for an individual good or service. This price is implicitly relative: it is intended to be compared with the prices of other products (for example, the price of pizza relative to the price of fried chicken). In contrast, the vertical axis of an aggregate supply and aggregate demand diagram expresses the level of a price index like the Consumer Price Index or the GDP deflator—combining a wide array of prices from across the economy. The price level is absolute: it is not intended to be compared to any other prices since it is essentially the average price of all products in an economy. The horizontal axis of a microeconomic supply and demand curve measures the quantity of a particular good or service. In contrast, the horizontal axis of the aggregate demand and aggregate supply diagram measures GDP, which is the sum of all the final goods and services produced in the economy, not the quantity in a specific market. In addition, the economic reasons for the shapes of the curves in the macroeconomic model are different from the reasons behind the shapes of the curves in microeconomic models. Demand curves for individual goods or services slope down primarily because of the existence of substitute goods, not the wealth effects, interest rate, and foreign price effects associated with aggregate demand curves. The slopes of individual supply and demand curves can have a variety of different slopes, depending on the extent to which quantity demanded and quantity supplied react to price in that specific market, but the slopes of the AS and AD curves are much the same in every diagram (although as we shall see in later chapters, short-run and long-run perspectives will emphasize different parts of the AS curve). In short, just because the AD/AS diagram has two lines that cross, do not assume that it is the same as every other diagram where two lines cross. The intuitions and meanings of the macro and micro diagrams are only distant cousins from different branches of the economics family tree.

Defining SRAS and LRAS

In the Clear It Up feature titled “Why does AS cross potential GDP?” we differentiated between short run changes in aggregate supply which the AS curve shows and long run changes in aggregate supply which the vertical line at potential GDP defines. In the short run, if demand is too low (or too high), it is possible for producers to supply less GDP (or more GDP) than potential. In the long run, however, producers are limited to producing at potential GDP. For this reason, we may also refer to what we have been calling the AS curve as the short run aggregate supply (SRAS) curve. We may also refer to the vertical line at potential GDP as the long run aggregate supply (LRAS) curve.

11.3 Shifts in Aggregate Supply

LEARNING OBJECTIVES By the end of this section, you will be able to:

• Explain how productivity growth changes the aggregate supply curve
• Explain how changes in input prices change the aggregate supply curve

The original equilibrium in the AD/AS diagram will shift to a new equilibrium if the AS or AD curve shifts. When the aggregate supply curve shifts to the right, then at every price level, producers supply a greater quantity of real GDP. When the AS curve shifts to the left, then at every price level, producers supply a lower quantity of real GDP. This module discusses two of the most important factors that can lead to shifts in the AS curve: productivity growth and changes in input prices.

How Productivity Growth Shifts the AS Curve

In the long run, the most important factor shifting the AS curve is productivity growth. Productivity means how much output can be produced with a given quantity of labor. One measure of this is output per worker or GDP per capita. Over time, productivity grows so that the same quantity of labor can produce more output. Historically, the real growth in GDP per capita in an advanced economy like the United States has averaged about 2% to 3% per year, but productivity growth has been faster during certain extended periods like the 1960s and the late 1990s through the early 2000s, or slower during periods like the 1970s. A higher level of productivity shifts the AS curve to the right, because with improved productivity, firms can produce a greater quantity of output at every price level. Figure 11.7 (a) shows an outward shift in productivity over two time periods. The AS curve shifts out from SRAS0 to SRAS1 to SRAS2, and the equilibrium shifts from E0 to E1 to E2. Note that with increased productivity, workers can produce more GDP. Thus, full employment corresponds to a higher level of potential GDP, which we show as a rightward shift in LRAS from LRAS0 to LRAS1 to LRAS2.

FIGURE 11.7Shifts in Aggregate Supply(a) The rise in productivity causes the SRAS curve to shift to the right. The original equilibrium E0 is at the intersection of AD and SRAS0. When SRAS shifts right, then the new equilibrium E1 is at the intersection of AD and SRAS1, and then yet another equilibrium, E2, is at the intersection of AD and SRAS2. Shifts in SRAS to the right, lead to a greater level of output and to downward pressure on the price level. (b) A higher price for inputs means that at any given price level for outputs, a lower real GDP will be produced so aggregate supply will shift to the left from SRAS0 to SRAS1. The new equilibrium, E1, has a reduced quantity of output and a higher price level than the original equilibrium (E0). A shift in the SRAS curve to the right will result in a greater real GDP and downward pressure on the price level, if aggregate demand remains unchanged. However, if this shift in SRAS results from gains in productivity growth, which we typically measure in terms of a few percentage points per year, the effect will be relatively small over a few months or even a couple of years. Recall how in Choice in a World of Scarcity, we said that a nation's production possibilities frontier is fixed in the short run, but shifts out in the long run? This is the same phenomenon using a different model.

How Changes in Input Prices Shift the AS Curve

Higher prices for inputs that are widely used across the entire economy can have a macroeconomic impact on aggregate supply. Examples of such widely used inputs include labor and energy products. Increases in the price of such inputs will cause the SRAS curve to shift to the left, which means that at each given price level for outputs, a higher price for inputs will discourage production because it will reduce the possibilities for earning profits. Figure 11.7 (b) shows the aggregate supply curve shifting to the left, from SRAS0 to SRAS1, causing the equilibrium to move from E0 to E1. The movement from the original equilibrium of E0 to the new equilibrium of E1 will bring a nasty set of effects: reduced GDP or recession, higher unemployment because the economy is now further away from potential GDP, and an inflationary higher price level as well. For example, the U.S. economy experienced recessions in 1974–1975, 1980–1982, 1990–91, 2001, and 2007–2009 that were each preceded or accompanied by a rise in the key input of oil prices. In the 1970s, this pattern of a shift to the left in SRAS leading to a stagnant economy with high unemployment and inflation was nicknamed stagflation. Conversely, a decline in the price of a key input like oil will shift the SRAS curve to the right, providing an incentive for more to be produced at every given price level for outputs. From 1985 to 1986, for example, the average price of crude oil fell by almost half, from $24 a barrel to $12 a barrel. Similarly, from 1997 to 1998, the price of a barrel of crude oil dropped from $17 per barrel to $11 per barrel. In both cases, the plummeting oil price led to a situation like that which we presented earlier in Figure 11.7 (a), where the outward shift of SRAS to the right allowed the economy to expand, unemployment to fall, and inflation to decline. Along with energy prices, two other key inputs that may shift the SRAS curve are the cost of labor, or wages, and the cost of imported goods that we use as inputs for other products. In these cases as well, the lesson is that lower prices for inputs cause SRAS to shift to the right, while higher prices cause it to shift back to the left. Note that, unlike changes in productivity, changes in input prices do not generally cause LRAS to shift, only SRAS.

Other Supply Shocks

The aggregate supply curve can also shift due to shocks to input goods or labor. For example, an unexpected early freeze could destroy a large number of agricultural crops, a shock that would shift the AS curve to the left since there would be fewer agricultural products available at any given price. Similarly, shocks to the labor market can affect aggregate supply. An extreme example might be an overseas war that required a large number of workers to cease their ordinary production in order to go fight for their country. In this case, SRAS and LRAS would both shift to the left because there would be fewer workers available to produce goods at any given price. Another example in this vein is a pandemic, like the COVID-19 pandemic. A pandemic causes many workers to become sick, temporarily reducing the supply of workers by a large amount. Further, workers might be cautious to go back to work in a pandemic because of health or safety concerns. While the shock to labor supply might not be permanent, it can cause a reduction in the supply of many goods and services, reflected in a leftward shift in the short-run aggregate supply curve. At various points during the COVID-19-induced pandemic, computer chips for automobiles, meat, and other consumer services were in short supply because of worker shortages around the world.

11.4 Shifts in Aggregate Demand

LEARNING OBJECTIVES By the end of this section, you will be able to:

• Explain how imports influence aggregate demand
• Identify ways in which business confidence and consumer confidence can affect aggregate demand
• Explain how government policy can change aggregate demand
• Evaluate why economists disagree on the topic of tax cuts

As we mentioned previously, the components of aggregate demand are consumption spending (C), investment spending (I), government spending (G), and spending on exports (X) minus imports (M). (Read the following Clear It Up feature for explanation of why imports are subtracted from exports and what this means for aggregate demand.) A shift of the AD curve to the right means that at least one of these components increased so that a greater amount of total spending would occur at every price level. A shift of the AD curve to the left means that at least one of these components decreased so that a lesser amount of total spending would occur at every price level. The Keynesian Perspective will discuss the components of aggregate demand and the

Simpler explanation — Cambridge AS & A Level Economics

Aggregate supply (AS) is the total planned supply of all the producers in the country. Economists sometimes differentiate between short-run aggregate supply (SRAS) and long-run aggregate supply (LRAS). Short-run aggregate supply is the output that will be supplied in a period of time when the prices of factors of production (inputs, resources) have not had time to adjust to changes in aggregate demand and the price level. In contrast, long-run aggregate supply is the output that will be supplied in the time period when the prices of factors of production have fully adjusted to changes in aggregate demand and the price level. The short-run aggregate supply curve The short-run aggregate supply curve slopes up from left to right as shown in Figure 17.5.

As the price level rises, producers are willing and able to supply more goods and services. There are three possible reasons for this positive relationship: The profit effect: As the price level (that is, the price of goods and services) increases, the prices of factors of production such as wages do not change. So as the price level rises, the gap between output and input prices widens and the amount of profit increases. The cost effect: It is assumed that wage rates, raw material costs and other input prices remain unchanged along an individual SRAS curve. However, average costs may rise as output increases.

This is because, for example, overtime payments may have to be paid and costs will be involved in recruiting more workers. To cover any extra costs that may be involved in producing a higher output, producers will require higher prices. The misinterpretation effect: Producers may confuse changes in the price level with changes in relative prices. They may think that a rise in the price they receive for their products indicates that their own product is becoming more popular. As a result, they may be encouraged to produce more.