5 Nevertheless, if the economy is already at full employment, then this boost is merely transitory: As economic activity rises above its sustainable level, wages and prices begin to rise, and the private sector's inflation expectations start to pick up. Of course, the central bank must eventually remove the policy stimulus to avoid a continuous upward spiral of inflation.
At that point, economic activity drops back to a sustainable level. However, inflation settles in at a permanently higher rate because prospects of future monetary expansions become embedded in expectations, and hence in wage and price adjustments, and the higher average inflation rate generates undesirable economic distortions.