1) Progressive tax rate, as a major concept in The Taxation, is frequently used in income tax.

2) The system of a four-grade progressive tax rate was adopted with 30% at the bottom level and 60% on the top level to reflect the State policies.

3) Progressive degree of progressive tax rate depends on the type of Social welfare function and labour supply elasticity.

4) How is the tax payable calculated with this progressive tax rate schedule?

5) It is in line with the fairness principle of levying on unearned income to change proportional tax rate to progressive tax rate in excess of specific amount.

6) The first part introduces the selection between the proportional tax rate and the progressive tax rate.