Calvo價格僵固模型下長期物價上漲率的影響

Long-Run Effects of Inflation Under Calvo Staggered Price Contract

長期物價上漲率在Calvo價格僵固模型下會產生兩種生產無效率，一是來自於平均加碼扭曲（average markup distortion），另一是來自於價格差異扭曲（price variation distortion）。前者指的是平均加碼高於邊際成本，造成總產出過少的無效率；後者指的是異質性中間財的價格差異造成中間要素僱用不平均的要素使用無效率。在典型的Calvo模型裡，價格的調整速度為外生，此時越高的長期物價上漲率只會強化兩種生產無效率，因此看不出維持長期物價上漲的任何好處。然而，當我們引入調整成本，內生化價格調整速度，微幅的長期物價上漲雖然會強化中間財的價格差異，卻可以降低平均加碼，而後者帶來的效率提升是有可能超過前著的效率損傷。本研究亦指出，若中間要素市場越競爭，則最適長期物價上漲率目標要越低。

Under Calvo staggered price contracts, there are two types of production inefficiency associated with long-run inflation. One is the average markup distortion that holds back the final production level from its social optimal level. The other is the price variation distortion due to the price erosion from inflation that inefficiently results in more social resources producing the same level of output. The standard Calvo model shows that inflation monotonically enhances both distortions, and therefore a positive long-run inflation target is not desired. However, when the price adjustment frequency is endogenous, the price adjustment speed increases with inflation. Without increasing much price adjustment frequency, minor inflation can erode vintage markups and pull down the average markup, with the output level pushing closer to the social optimum. This partially corrects the average markup distortion. When the inflation rate is low, this gain can outweigh the loss from price variation distortion. We also find that the more competitiveness there is among producers, the lower the optimal long-run inflation target shall be.