A flat tax is an example of a proportional tax.

单一税就是比例税的一个例子。

A proportional tax upon this particular article of expense might, perhaps, produce a more considerable revenue than any which has hitherto been drawn from it in any part of Europe.

对这种特殊的消费品按比例征税，也许会产生比欧洲任何地方迄今从中提取的任何收入都多的收入。