Slaves were in the tradition of shinuhi (privately-owned slave) and buqu (a serf) and until the Tang dynasty they had played an important role in the labor service in shoens, but in the Sung dynasty the cultivation by denko cost less for the owners and the managers and gradually the labor was charged to denko and slaves progressively became employees.
奴隷は前時代の私奴婢・部曲の流れを汲み、唐代までは荘園内の労働において重要な役目を担っていたが、宋代になると佃戸による耕作の方が所有者・管理者の負担が軽く、次第に佃戸に切り替えられたり、奴隷の雇傭者化が進むことになっていった。