摘要：

This study investigates the welfare effects of monetary policy responses to external shocks in a small open economy characterized by firm heterogeneity. Through a Dynamic Stochastic General Equilibrium (DSGE) model incorporating Rotemberg-type price adjustment costs, it analyzes five monetary policy rules, ranging from traditional monetary targeting to extended Taylor rules. The findings reveal that firm heterogeneity significantly influences policy transmission through market entry/exit and export decisions. Various shocks (technological, external demand, inflation, and interest rates) yield distinct impacts on exchange rates, firm numbers, and output levels. The results indicate that money quantity rules are more effective than interest rate rules in stabilizing economic variables against external shocks, while considering exchange rate stability in monetary policy enhances welfare for small open economies. These insights are particularly relevant for economies like Taiwan, where policy effectiveness largely depends on understanding and accounting for firm-level heterogeneity.