在線性所得稅制的無窮生命代表性個人模型，Chamley (1986)和Judd (1985)已經證明長期的最適資本稅爲零。本篇研究一個除了累進稅制外其餘設定都相同的模型，結果如下。首先，累進稅制下的長期最適資本所得稅爲正。其次，累進稅制下由當前稅率改制爲正最適所得稅率的福利利得大於線性稅制下改制爲零資本所得稅率的福利利得。我們的發現支持自19世紀後期之後，採行累進稅制的先進國家課徵資本稅。

In infinitely lived, representative-agent models with linear income taxes, the influential studies by Chamley (1986) and Judd (1985) have shown that the optimal capital tax is zero in the long run. Our paper uses a similar model with progressive taxes and the results are as follow. First, the long-run optimal capital income tax is positive with progressive income taxes. Second, the welfare gain from moving current tax rates toward positive optimal income taxes with progressive tax rates is larger than moving toward a zero capital income tax with linear income taxes. Our findings lend support to positive capital income taxes under a system of progressive income taxes adopted in developed countries since the late 19th century.