Sang's skill at economic policy would only come into play during the middle of Emperor Wu's reign. By then, the ongoing campaigns against the Xiongnu had drained the wealth built up by Emperor Wu's predecessors, and the state had entered a financial crisis. In 120 BC, the Minister of Agriculture, Zheng Dangshi, first proposed the idea of state monopolies on iron and salt, recommending two powerful salt and iron magnates to join the government and manage the industry on a national scale. Sang Hongyang was then assigned to aid the magnates in their planning. With the success of the monopolies in improving the empire's financial situation, Sang eventually rose to become Assistant Minister of Agriculture.