At a minimum, the present paper should serve as a warning against
too easy an acceptance of the view that the costs of sustained inflation
are small relative to the costs of unemployment. If a temporary reduction
in unemployment causes a permanent increase in inflation, the present
value of the resulting future welfare costs may well exceed the temporary
short-run gain. Previous analyses have underestimated the cost of a
permanent increase in the inflation rate because they have ignored the
growth of the economy and therefore the g~owth of the future instantaneous
welfare costs. In the important case in which the growth of aggregate
income exceeds the social discount rate, no reduc~ion in unemployment can
justify any permanent increase in the rate of inflation. Quite the
contrary, if the inflation rate is above its optimal level, the economy
should then be deflated to reduce the inflation rate regardless of the
1 temporary consequences for unemployment.