The nine rank system, also known as the nine grade controller system, was used to categorize and classify government officials in Imperial China. Prior to the Nine ranks, official positions were denoted by their salary paid in number of bushels of grain. For example, during the Han dynasty the highest-ranking officials were classed as wandan (萬石), meaning ten thousand bushels, and were paid 350 bushels of grain per month. The lowest ranking petty sub-officials were paid in pecks, worth less than 100 bushels per year.
The Nine rank system was created after the end of the Han in 220 AD when Chen Qun, a court official from the state of Cao Wei, proposed it as a way of organizing the state bureaucracy. It was called the "Nine rank method for recruiting men for office" (Jiu pin guan ru fa; 九品官入法). During the Song dynasty it became the "system of Nine ranks and impartial judges."
The Nine ranks were separated into Upper, Middle, and Lower classes, each composed of three ranks, making nine in total. Each rank was also further classified into standard and secondary ranks, so that the entire system contained 18 ranks.
During the Northern Wei, ranks four to nine added additional upper and lower ranks to the standard and secondary ranks, giving the Nine ranks system a total of 30 ranks (6 in the top 3 ranks; 24 from ranks 4 to 9).
Ranks were expressed thus:
正一品 (Zheng yi pin; Standard class, Rank 1),
從一品 (Cong yi pin; Secondary class, Rank 1),
正四品上 (Zheng si pin shang; Standard class, Rank 4, Upper grade),
從四品下 (Cong si pin xia; Secondary class, Rank 4, Lower grade).
Aside from official ranked titles, officials also received prestige titles (散官). They were normally based on seniority.
There are no poor people in the upper ranks and no powerful families in the lower ones.— A common saying during the Song dynasty, Jinshu: 45: 1274
The primary avenues to entering the nine ranks were through sponsorship, recommendation (zheng pi; 征辟) and examination (cha ju; 察舉). Recommendations were made by local recruiters (Zhongzheng; 中正) based on social status, morals, and ability, of which social status soon became the most important criterion. During the Sui and Tang dynasties recommendations were marginalized and phased out of the recruiting process, although sponsorship continued to play an important part in reaching the examinations until the Song. In the Song era, candidates were able to present themselves for exams independently, and bureaucratic staff recruited directly through the imperial examination system became the norm.
The current Chinese cadre ranking system is loosely based on this historical system.