4 Inflation-employment trade-off
This section explains how a move from a NMP regime, i.e. a setup where each country has
its own CB setting the money supply, to a MU with a common CB may affect the trade-off
between inflation and employment for the CB. Henceforth we base the comparison on the
results obtained under a NMP regime in Cuciniello (2007).
In setting her optimal monetary policy the CB faces a trade-off between inflation and
employment. Since all firms have the same reaction function, from cost minimization we
achieve the following aggregate demand for labor
1 1„ ∖ a
Lc = (Yc) “ = Ç-1 j , c ∈ [H, F] (23)
where the second equality stems from equation (13) and (14). Then taking logs and
plugging equation (20) into equation (23) yields
lc ≡ log Lc = m. - ωc. (24)
Now the MU Phillips curve is obtained by solving for money supply equation (24) and
substituting it into (22),
πu = (1 - a)lu + ωu (25)
where lu ≡ 7⅛ +(1 — 7)lp. The slope of the Phillips curve in the MU is hence
d~ιu
"dlU^ = 1 — « 0. (26)
It can be shown16 that under a NMP regime the slope of the Home Phillips curve is given
by,
d"N n
= 1 — «7 > 0. (27)
aι∏
It is apparent that the slope of the Phillips curve depends on the monetary regime set
up in the country as the following proposition summarizes.
Proposition 1 The formation of a MU leads a change in the trade-off between inflation
and employment faced by the CB so that the Phillips curve is flatter in the MU, ^fff^ > ^fff^-.
Intuitively, the impact of money supply on aggregate employment is always equal to
one (see equation (24)). Conversely, the general level of price is affected differently by the
CB in a MU and under a NMP. Under floating exchange rates, the Home CB influences
the CPI via the producer price index and the nominal exchange rate. In a MU this second
channel is ruled out. The Proposition 1 simply states that the two channels of transmission
16See Cuciniello (2007).
10