译者所关注的证据是税率效果和收入效果的结合。

And the evidence that Romer and Romer look at is combining the tax rate stuff with the income stuff.

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这项税收对增加收入没有太大效果。

The tax is unlikely to add much to its revenue.

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然而，很多出租车司机称这两个选择中的任何一个对帮助他们提高收入的效果都是有限的。

However, many taxi drivers say the effectiveness of either option to help raise their income is limited.

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