出版社：Bank of Japan, Institute for Monetary and Economic Studies
摘要：It is well known that the concept of “determinacy”—a single stable solu-
tion—plays a major role in contemporary monetary policy analysis. But
while determinacy is desirable, other things equal, it is not necessary
for a solution to be plausible and is not sufficient for a solution to be
desirable. There is a related but distinct criterion of “learnability” that
seems more crucial. This paper argues that recognition of information
feasibility requires that a candidate solution must, to be plausible, be
quantitatively learnable on the basis of information generated by the
economy itself. Since a prominent least-squares (LS) learning process
is highly “biased” toward learnability, it is reasonable to regard it as
a necessary condition for any specific solution to be relevant. This im-
plies that determinacy is not necessary for policy analysis; there may
be more than one stable solution, but only one that is LS learnable.
Also, determinacy is not sufficient for satisfactory policy analysis; ex-
plosive solutions pertaining to nominal variables will not be eliminated
by transversality conditions. For these and other reasons, the role of
determinacy in monetary policy analysis should be reconsidered and
substantially de-emphasized.
