8. Consider the AE/PC model with time lags. Suppose the economy starts in 2019
with output at potential and constant inflation. In 2020, an adverse supply shock oc-
curs, shifting the Phillips curve up.
a. Show the paths of output and inflation over time if the central bank keeps the
real interest rate constant.
ANSWER: An adverse supply shock does not shift the AE curve. With constant real
interest rates, aggregate expenditures are unchanged after the supply shock. Output
is constant and remains at potential, but the inflation rate will permanently rise in re-
b. Can the central bank prevent inflation from rising temporarily as a result of the
supply shock? Can it prevent inflation from rising permanently? Explain.
ANSWER: Let’s assume that the Fed did not anticipate the supply shock and that the
supply shock occurs in 2020 only. In 2021, the PC shifts back to its original position.
Given those assumptions, the Fed cannot prevent inflation from rising temporarily in
c. Suppose policymakers want to return inflation to its 2019 level as quickly as
possible and then keep inflation constant. What path should policymakers choose
for the real interest rate? What are the resulting paths of output and inflation?
ANSWER: Policymakers should increase the real interest rate in 2020, immediately
after the supply shock was observed. In 2021, policymakers should reduce the real
ONLINE AND DATA QUESTIONS
www.worthpublishers.com/ball2
9. From the text Web site, get Bernanke and Kuttner’s data on expected and unex-
pected changes in the federal funds rate by the FOMC. (You may have used these
data to solve Problem 3.12.) Choose one day when the expected change in the funds
rate was large and the unexpected change was small, and one day when the oppo-
site was true. Then link to the site of the Federal Reserve Bank of St. Louis, which
A-90 CHAPTER 13 Economic Fluctuations, Monetary Policy, and the Financial System