Zhuanque, state monopoly, means the state keeping the production and sale of a commodity to itself. In the Yuanshou years of Emperor Wu of Han (about 119 BCE), salt and iron were put under official management, with the state holding the production and sale of both.
The gains and losses of the monopoly were already argued over in the Han. In 81 BCE the Salt and Iron Conference was held, where the worthies and literati debated the merits of the monopoly with Sang Hongyang, and the record of the debate was later compiled as the Discourses on Salt and Iron.
In the Qianyuan years of the Tang (758), Diwu Qi put the salt monopoly law into effect, and revenue from salt became a pillar of state finances in the later Tang and in the dynasties after. Besides the monopoly, the duties levied at passes and at the offices for overseas trade were also part of the state's income.
Salt & Transit Monopolies is the class in the chapter on Commerce on state monopolies and the taxes on passes and markets. The state took everyday goods such as salt and iron into official hands, and also levied duties at passes and at the offices for overseas trade, and drew revenue from both.
