摘要：Many recent empirical studies have reported that the passthrough from
money-market rates to retail lending rates is far from complete in the euro
area. This paper formally shows that when only a fraction of all the loan rates
is adjusted in response to a shift in the policy rate, fluctuations in the
average loan rate lead to welfare costs. Accordingly, the central bank is
required to stabilize the rate of change in the average loan rate in addition to
inflation and output. It turns out that the requirement for loan rate
stabilization justifies, to some extent, the idea of policy rate smoothing in
the face of a productivity shock and/or a preference shock. However, a drastic
policy reaction is needed in response to a shock that directly shifts retail
loan rates, such as an unexpected shift in the loan rate premium.
