income tax rates for corporate income 對(duì)不同的收入有不同的marginal tax rate. 為什么會(huì)有不同?
不同taxable income中,marginal tax rate從15%,25%,34%,39%,34%,35%,38%,最后到35%.
其中,為什么一開始從15%一直升到39%之后又下降了呢?為什么后來又略有上升?
（is to make sure that firms that have very high taxable income don't benefit from the lower rates on the initial dollars that they earn.）《——書上的原話,可以具體解釋一下或者舉例說明一下嗎?
謝謝
核心問題：為什么marginal tax rate從一開始的15%升到39%后，又有小浮動(dòng)變化？