An optimizing model, with a flexible-price sector and a sticky-price sector
, is presented to analyze the effects of relative-price changes on inflatio
n fluctuations. The relative price of the flexible-price good represents a
shift parameter of the New Keynesian Phillips curve. The optimal monetary p
olicy is to target sticky-price inflation, rather than a broad inflation me
asure. Although stabilizing the relative price around its efficient value i
s one of the appropriate goals of the central bank, stabilizing sticky-pric
e inflation is sufficient for achieving this goal. An optimal monetary poli
cy for a small open economy is also discussed. (C) 2001 Published by Elsevi
er Science B.V.