11.5 How the ad/as model incorporates growth, unemployment, and  (Page 3/15)

An alternative source of inflationary pressures can occur due to a rise in input prices that affects many or most firms across the economy—perhaps an important input to production like oil or labor—and causes the aggregate supply curve to shift back to the left. In [link] (b), the shift of the SRAS curve to the left also increases the price level from P ₀ at the original equilibrium (E ₀ ) to a higher price level of P ₁ at the new equilibrium (E ₁ ). In effect, the rise in input prices ends up, after the final output is produced and sold, being passed along in the form of a higher price level for outputs.

The AD/AS diagram shows only a one-time shift in the price level. It does not address the question of what would cause inflation either to vanish after a year, or to sustain itself for several years. There are two explanations for why inflation may persist over time. One way that continual inflationary price increases can occur is if the government continually attempts to stimulate aggregate demand in a way that keeps pushing the AD curve when it is already in the steep portion of the SRAS curve. A second possibility is that, if inflation has been occurring for several years, a certain level of inflation may come to be expected. For example, if consumers, workers, and businesses all expect prices and wages to rise by a certain amount, then these expected rises in the price level can become built into the annual increases of prices, wages, and interest rates of the economy. These two reasons are interrelated, because if a government fosters a macroeconomic environment with inflationary pressures, then people will grow to expect inflation. However, the AD/AS diagram does not show these patterns of ongoing or expected inflation in a direct way.

Importance of the aggregate demand/aggregate supply model

Macroeconomics takes an overall view of the economy, which means that it needs to juggle many different concepts. For example, start with the three macroeconomic goals of growth, low inflation, and low unemployment. Aggregate demand has four elements: consumption, investment, government spending, and exports less imports. Aggregate supply reveals how businesses throughout the economy will react to a higher price level for outputs. Finally, a wide array of economic events and policy decisions can affect aggregate demand and aggregate supply, including government tax and spending decisions; consumer and business confidence; changes in prices of key inputs like oil; and technology that brings higher levels of productivity.

The aggregate demand/aggregate supply model is one of the fundamental diagrams in this course (like the budget constraint diagram introduced in the Choice in a World of Scarcity chapter and the supply and demand diagram introduced in the Demand and Supply chapter) because it provides an overall framework for bringing these factors together in one diagram. Indeed, some version of the AD/AS model will appear in every chapter in the rest of this book.

Key concepts and summary

Cyclical unemployment is relatively large in the AD/AS framework when the equilibrium is substantially below potential GDP. Cyclical unemployment is small in the AD/AS framework when the equilibrium is near potential GDP. The natural rate of unemployment, as determined by the labor market institutions of the economy, is built into what is meant by potential GDP, but does not otherwise appear in an AD/AS diagram. Pressures for inflation to rise or fall are shown in the AD/AS framework when the movement from one equilibrium to another causes the price level to rise or to fall. The balance of trade does not appear directly in the AD/AS diagram, but it appears indirectly in several ways. Increases in exports or declines in imports can cause shifts in AD. Changes in the price of key imported inputs to production, like oil, can cause shifts in AS. The AD/AS model is the key model used in this book to understand macroeconomic issues.

References

Library of Economics and Liberty. “The Concise Encyclopedia of Economics: Jean-Baptiste Say.” http://www.econlib.org/library/Enc/bios/Say.html.

Library of Economics and Liberty. “The Concise Encyclopedia of Economics: John Maynard Keynes.” http://www.econlib.org/library/Enc/bios/Keynes.html.

Organization for Economic Cooperation and Development. 2015. "Business Tendency Surveys: Construction." Accessed March 4, 2015. http://stats.oecd.org/mei/default.asp?lang=e&subject=6.

University of Michigan. 2015. "Surveys of Consumers." Accessed March 4, 2015. http://www.sca.isr.umich.edu/tables.html.