period after scaling this up by the rate of inflation observed in the previous
period. Therefore, the log-linearised index of output prices is given by,
pbtd = αpbtd-1 +(1- α)pbtr
where ptr is the average reset price in period t and is given by,
pbtr =(1- ω)xbt + ωpbtb
(20)
(21)
ω is the proportion of firms following the rule of thumb, and ptb is the price set
set according to the rule of thumb,
br d
pbt = pbt-1 + πbt-1.
Substituting equation (22) into (21) gives,
pbtr =(1- ω)xbt + ωpbtr-1 + ωpbtd-1 - ωpbtd-2 .
Inserting equation (20) into this expression then yields,
Pt
1-α
αPt-1
1-α
(1 - ω)xt+ω μ t- 1—
1-α
αP*-2
1-α
+ωpbt-1 - ωpbt-2.
(22)
(23)
(24)
This can be rearranged in terms of xbt, substituted into equation (22) and solved
using the definition of output price inflation, πbt = pbtd - pbtd-1 to give,
d
πbt
βα E bd +ωbd +(1 - ω)(1 - a)(1 - αβ) (dC f254)
λ Etbt+1 + λbt-1 + (1 + (ψ - 1)θ)λ (MC* (25)
+(ψ - 1)byet + Pbt - pbtd).
where λ = ω + βωα + α - ωα .
2.4 Open Economy NKPC
We next reformulate the above specification in a form more appropriate for
estimation. To do so consider the element of marginal cost which is independent
of the firm’s actions,
1-ρ
MgCt =
+ αm
(26)
This can be log-linearised as,
_____
MgCt
pf wff αm∖ρ
______w_______w. + P-V ONl____(pf _ P )
W + pf (wf Om ´'´ ‘ + (w + pf W Om П (p* ')
4 P ∖ αN JJ ∖ P ∖ αN J J
(27)