Progressive tax（累进税）

A progressive tax imposes a higher percentage rate on taxpayers who have higher incomes. 

On the pro side, a progressive tax system reduces the tax burden on the people who can least afford to pay. That leaves more money in the pockets of low-wage earners, who are likely to spend all of that money on essential goods and stimulate the economy in the process. A progressive tax system also tends to collect more taxes than flat taxes or regressive taxes, as the highest percentage of taxes is collected from the highest amounts of money.

累进税指随着应税额增大，税率逐渐累进升高。

累进税的优点在于，可以减轻低收入者的纳税负担，刺激经济发展。此外，相较于单一税和累退税，累进税往往可以征收更多的税，原因在于可以对较高收入者采用较高级别的税率。

我国《个人所得税》第三条第一段和第二段规定，综合所得适用百分之三至百分之四十五的超额累进税率，经营所得适用百分之五至百分之三十五的超额累进税率。（超额累进税率（excess progressive tax rate）是累进税率的一种，以征税对象的超额部分为基础计征税款，征税对象数额超过某一等级时，仅就超过部分按高一级税率计算征税。）

以经营所得为例，全年应纳税所得额不超过30000元的，税率为5%；超过30000元至90000元的部分，税率为10%；超过90000元至300000元的部分，税率为20%；超过300000元至500000元的部分，税率为30%；超过500000元的部分，税率为35%。

Proportional tax（比例税）

A proportional tax is an income tax system that levies the same percentage tax to everyone regardless of income. A proportional tax is the same for low, middle, and high-income taxpayers. Proportional taxes are sometimes referred to as flat taxes.

比例税指不论征税对象数量或金额的多少，统一按一个百分比征税，有时也被称为“flat tax”，即单一税。

比例税计算简便，对同一征税对象适用一个比例，有利于鼓励竞争，实行规模经营。

我国《个人所得税》第三条第三段规定，利息、股息、红利所得，财产租赁所得，财产转让所得和偶然所得适用比例税率，税率为百分之二十。

Regressive tax（累退税）

A regressive tax is a tax applied uniformly, taking a larger percentage of income from low-income earners than from high-income earners. It is in opposition to a progressive tax, which takes a larger percentage from high-income earners.

Low-income individuals pay a higher amount of taxes compared to high-income earners under a regressive tax system. That's because the government assesses tax as a percentage of the value of the asset that a taxpayer purchases or owns. This type of tax has no correlation with an individual's earnings or income level.

Regressive taxes include property taxes, sales taxes on goods, and excise taxes on consumables, such as gasoline or airfare. Excise taxes are fixed and they're included in the price of the product or service.

累退税指随课税对象数额或相对比例的增大而逐级降低税率，是“累进税”的对称。

在此情况下，相较于高收入者，低收入者缴纳的税款更高，这是因为政府是按纳税人所购买或拥有资产价值的一定比例课税。

累退税是指税额相对于纳税人净收入的比例而言，而不是指税额相对于课税对象的比例。

累退税包括财产税、销售税、消费税等。

参考：

Investopedia；

百度百科；

MBA智库·百科