ECON6002 Tutorial 6 (Nominal Rigidity)
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ECON6002
Tutorial 6 (Nominal Rigidity)
1. Consider the problem facing a household/firm in the Lucas model when P is unknown. The agent chooses Li to maximize the expectation of Ui = Yi - Yiy conditional on Pi .
(a) Find the first-order condition for Yi and rearrange it to obtain an expression for Yi in terms of E[Pi/P]. Take logs of this expression to obtain an expression for yi .
(b) How does the amount of labour that the individual supplies if he or she follows the certainty-equivalence rule yi = E[ln(Pi/P)IPi] compare with the optimal amount derived in part (a)? (Hint: How does E[ln(Pi/P)] compare with lnE[Pi/P]?)
(c) Suppose that, as in the Lucas model, ln(Pi/P) = E[ln(Pi/P)IPi] + ui, where ui ~ N(0, σu(2)), with σu(2) independent of Pi . Show that this implies that ln{E[(Pi/P)IPi]} = E[ln(Pi/P)IPi] + c, where c is a constant whose value is independent of Pi . (Hint: Note that Pi/P = exp{E[ln(Pi/P)IPi]}exp(ui), and show that this implies that the yi that maximizes expected utility differs from the certainty-equivalence rule only by a constant. Note also that if X ~ N(µ, σ2 ), then E[ex ] = eu e口2 /2 .)
2. The Lucas imperfect-information model yields an aggregate-supply curve: y = b(p - E[p]) and an aggregate-demand curve: y = m - p
(a) Solve the two curves together to get expressions for y and p in terms of m and E[p]. (b) Take expectations of the p equation and solve for E[p].
(c) Plug the formula you calculated for E[p] into the expressions you got in part (a) to get final equations for y and p in terms of m and E[m].
2023-07-12