1. The objective reason is that the war led to social unrest and economic depression.

The subjective reason is that the rulers in the early Han dynasty learned the lesson of Qin's death.

2. Emperor Gaozu, Emperor Wendi and Emperor Jingdi adopted the policy of clearing taxes and paying taxes to persuade farmers to reduce rents.

3. The rule of Wenjing appeared in Wendi and Jingdi. The unification of Emperor Wu of Han Dynasty.