傳統理論認為，對資本課徵所得稅使資本報酬降低，導致儲蓄 與投資減少，進而不利於經濟成長。為促進成長，北歐國家自1990 年代初期開始陸續實施雙元所得稅制改革，其最主要的特色在於對 資本所得課以較低的比例稅，而勞動所得則維持累進稅制。我們採 用差異中差異配對分析方法來檢驗雙元所得稅制是否較其他稅制更 有益於經濟成長。我們採用全球167 個國家為研究樣本，發現實施 雙元所得稅制對經濟成長有顯著之正向影響。因此，本文之實證結 果對雙元稅制有助於促進經濟成長之觀點提供新的實證證據。

The traditional theory argues that capital income taxation decreases capital returns. Therefore, such taxation results in lower savings and investments, and hence slower growth. To promote growth, Nordic countries have begun to implement the dual tax income system since the early 1990s. The dual income tax system levies a lower flat tax rate on capital income, while it maintains a progressive tax rate on labor income. We employ the difference in differences with matching model to examine if the dual income tax system is more beneficial to economic growth than other tax systems. Using data on 167 countries, the empirical results show that the effect of the dual income tax system on growth is statistically positive. Our empirical findings suggest that the dual income tax system enhances growth.