本文利用一個新凱因斯模型，探討市場區隔的假設之下，名目僵固的程度對貨幣政策的效果有何影響。本文探討了貨幣供給政策與名目利率的短期關係，亦即流動效果，同時也探討了當貨幣政策為泰勒式的利率法則時，貨幣政策的效果。本文的結果發現，價格僵固與工資僵固的假設，對模型所得出的流動效果有不同的作用。價格僵固可使模型得出的流動效果在短期內更加顯著，而工資僵固並無此作用。但若加入工資僵固的假設，可使原來在價格僵固假設下所得出的流動效果變得更有持續性。本文結果亦顯示，在市場區隔的新凱因斯模型中，名目僵固的假設可使模型得出的貨幣政策的產出效果與一般實證研究的發現更為一致。而且，不論貨幣政策是採貨幣供給法則或是泰勒式的利率法則，引進工資僵固的假設均使得貨幣政策的產出效果加大。

In this thesis I explore the relationships between nominal rigidities, market segmentation, and monetary policy in new Keynesian (NK) models. Specifically, I investigate how the presence of nominal rigidities affects the liquidity effect---a positive short-run relationship between money supply and nominal interest rates that has been found in the data, and I also study the effects of money policy on the economy, especially when the policy follows a Taylor’s (1993) rule. The results suggest that different assumptions on nominal rigidities may help the model capture the liquidity effect in different ways. Specifically, introducing the rigidity on commodity prices into the NK models may help the models generate stronger liquidity effects, while introducing the rigidity on nominal wage rates into the models may increase the persistence of the liquidity effect generated by the models. The results also suggest that for the NK models with market segmentation, the presence of nominal rigidities may help the models better explain the effects of monetary policy that have been suggested by previous empirical studies. Meanwhile, the results reveal that introducing wage rigidity into the models may enlarge the effect of monetary policy---either a rule on monetary growth rate or on nominal interest rate---on real output.

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