''Class system in the Yuan Dynasty'
Notoriously, the Mongols imposed a four class system on China that divided the population into four separate ethnic groups. These had a descending order of privilege and were to become a cause of much contention. The Mongols placed themselves first, then Western and Central Asians who were known as semu ren. Next were the Han ren, who were the people of Northern China and conquered in 1234. These included Chinese and Qidan, Jin and others. The final group and of the lowest order were the nan ren, the people who had been ruled by the Southern Song and brought into the new Mongol Empire in 1279. The class distinctions were not too rigidly enforced but they did have implications when it came to privileges, appointments and taxation.
In the past, the Chinese had allowed ethnic communities to punish offenders according to their own laws. In the Yuan period Mongols and semu ren were tried according to Mongolian or Central Asian laws, while the Chinese were tried according to Chinese law. This resulted in a diverse system of punishments. Special courts were established to deal with cases involving more than one ethnic group. While the Mongols continued to receive certain advantages, in marital disputes the law was applied according to the husbands group. However, if the wife happened to be a Mongol, in that case her ethnicity took preference.So far as the tax system was concerned, then the Mongols did exploit the Chinese. Under Ogodei harsh taxes were replaced by a more orderly system proposed by Yeluchucai. But his reforms were to be replaced by tax-farming by Muslim entrepreneurs. Earlier disruptions in the North through conflict and natural disasters led to an apparently excessive tax burden upon those living there. In the South, although the Mongols enjoyed concessions, the Chinese population fared somewhat better than their Northern compatriots and landowners may well have benefited from the Yuan economic policies.