本研究主要探討在小型開放經濟體下的最適貨幣政策，主要以新凱因斯模型在完全資本市場的假設之下，探討資本稅的可行性對總體經濟變數的影響。開放經濟下由於外部扭曲(external distortion)的存在，完全穩定國內通貨膨脹的政策就並非最適。本研究發現當兩國商品的替代彈性趨於無窮大時，封閉和開放經濟之間的政策差異就會消失。
從數值分析結果來看，最適貨幣政策的設計主要取決於是否課徵資本稅。若資產交易所帶來的不效率可以透過課徵資本稅來抵銷，則在最適貨幣政策之下國內通貨膨脹的變動幅度較小；反之，若政府無法最適的調整資本稅，則國內通貨膨脹的波動幅度將較大。本文亦發現，過去文獻在探討最適貨幣政策普遍未考慮經常帳方程式的做法，可能會導致虛假的結果產生。

This paper analyzes the optimal monetary policy in small open economies featuring monopolistic competition and nominal rigidity. Due to the presence of the external distortion, the optimal monetary policy in a small open economy can deviate from its closed-economy counterpart in that complete domestic inflation stabilization is not optimal in general. The policy discrepancy between closed and open economies vanishes if the elasticity of substitution between domestic and foreign goods goes to infinity.

The numerical results suggest that the design of optimal monetary policy depends crucially on whether a corrective asset tax is available. If the inefficiency in asset trading can be eliminated by an asset tax the optimal monetary policy exhibits little volatility in domestic inflation. In contrast, the optimal volatility of domestic inflation becomes much greater when an asset tax is unavailable.

This paper also shows that the common practice that excludes the current-account equation from the optimal policy problem may lead to spurious results.

1 Introduction 1
2 The model 5
2.1 The households 5
2.2 The government 9
2.3 The equilibrium 10
3 The optimal policy problem 11
4 Numerical analysis 15
4.1 Calibration 15
4.2 Optimal monetary policy when asset tax is available 16
4.2.1 Impulse responses analysis 17
4.2.2 Volatility of domestic inflation 17
4.2.3 Volatility of real exchange rate 18
4.3 Optimal monetary policy with zero asset tax 18
4.3.1 Impulse responses analysis 18
4.3.2 Volatility of domestic inflation 19
4.3.3 Volatility of real exchange rate 20
4.4 Comparisons with the domestic inflation targeting rule 20
5 Conclusion 21
References 33
A Appendix 35
A.1 First-best allocation and efficient steady state 35
A.2 Suboptimal monetary policy 37

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