不太明白这个，assume存入取出时tax=20%， 回报率10%, 本金$100

401k: 100+10=110, 110*80%=88

roth:100*80%=80, 80+8=88

两个不是equal吗?

所以<5年roth 和 traditional 没有什么区别，(当然不是向你上面这个简单的算法， 但是结果差不多)。

长期就不一样了， 简单的说， compound 的收益不用交税这个时间越久， 越能体现出来， 我这里没有具体的就算方法， 你可以上网search 一下。

当然这个里面都有一个assumption, 就是很多年以后，税率不比现在低， 而且你的收入在退休后和现在的差别不是太大。

another point is that the tax bracket could be higher than current rate in the future.

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