???? Many ethnic groups based their livelihood on animal husbandry and achieved great skill in raising horses, sheep and other livestock. This contributed to the development of a diversified economy in the country as the Hans were mainly farmers. Horse-raising by the Xiongnus and their ancestor tribe, the Northern Kunyi in ancient China, reached a fairly high level; they spread their knowledge of raising horses, mules and donkeys to the Central Plains peoples, exerting an enormous influence on the development of their agriculture and livestock breeding, and on the development of a system of stage coaches. Historical records show enormous numbers of livestock of the ethnic minorities being steadily drawn to the Central Plains. In one barter the Turk made with the Sui Dynasty, 10,000 horses and 20,000 sheep were involved; 140,000 bolts of silk cloth were exchanged every year for Turkish livestock by the Tang. The Wuman and Baiman people were nationally known for their fine "Dali" horses -- several thousand of the breed were imported every year into Yongzhou and the Central Plains during the Song. During the reign of Emperor Shen Zong (1573-1620) of the Ming Dynasty, 36,000 Mongolian horses were sold in the town of Zhangjiakou every year. In the Qing Dynasty there was a sale of 100,000 horses and as many as 500,000 sheep made by the Mongolian Khalkhas.