ECON6002 Tutorial 9 (Time Inconsistency)
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ECON6002
Tutorial 9 (Time Inconsistency)
1. Suppose aggregate supply has the simple form:
y = yn + (m − me) + e
where y , m , yn , me , and e are aggregate output, inflation, flex-price output, inflation expecta- tions, and an aggregate supply shock, respectively. Assume that the shock is i.i.d. with mean E[e] = 0 and variance uro(e) = 72 .
The central bank has a loss function that is different to the social loss function (i.e., the loss function corresponding to the utility of households). In particular, the central bank has discretion to set inflation m in order to minimize:
LCB = (y − y\ )2 + r\ (m − m* )2
subject to the aggregate supply constraint. Note, y\ is the central bank’s output target, m* is the central bank’s inflation target, and r\ > 0 reflects the central bank’s preference for stabilizing inflation. The timing of events is as follows: First, households/firms form inflation expectations me using rational expectations. Then the shock e is realized and the central bank chooses the level of inflation m to minimize its loss LCB .
The social loss function is:
Lsociety = (y − y* )2 + r(m − m* )2
where y* > yn is the socially optimal level of output and r > 0 reflects households’ relative preference for stabilizing inflation around m* .
(a) For a given level of me , compute the inflation rate m that the central bank will set.
(b) Under rational expectations, compute inflation expectations me , inflation m, and output y . Provide intuition for how the effects of the shock e on inflation and output depend on r\ .
(c) Suppose the central bank targets the socially optimal level of output, i.e. y\ = y* . Explain what level of a\ would make the inflation target m* more credible and what level of what a\ would provide the central bank with the greatest flexibility in terms of stabilizing output. Does a “hawkish” central bank with a\ >> a induce a tradeoff between credibility and flexibility?
(d) Show that < 0 if 72 = 0. What does this imply for the optimal degree of central bank “hawkishness” a\ ? (Hint: = E ┌ (y − y* ) + a\ (m − m* ) + E[(m − m* )2]].)
2023-07-13