本文設定一涵蓋浮動匯率、單純雙元匯率、及雙元浮動匯率等體制的小型開放經濟模型，據以探討民眾通貨多元化的持有是否將妨礙各種匯率體制的隔絕功能。本文發現，在以上三種匯率制度當中，只有雙元浮動匯率制度方能讓本國的實質部門免於遭受國外通貨膨脹的波及。

　　　　　This paper develops a general macromodel which is able to describe avariety of exchange regimes, including flexible exchange rates, ordinary two-tier exchange rates, and two-tier float exchange rates. The main purpose of the analysis is to examine the insulation function of eachexchange-rate system in the presence of currency substitution. The majorfinding is that, among three exchange-rate systems, the two-tier floatregime is the unique system which can provide complete insulation fromforeign inflation.