However, in Japan the saka system, in which the ko (an administrative unit of a few families under the Ritsuryo system) was classified by rank and the labor was allocated according to rank, was not adopted and therefore the zoyo, free of rank, was mandated.
しかしながら、雑徭はその補完でしかない（日本は戸を等級で分けて等級ごとに負担する労役を定める差科制を採らなかった為に等級に依らない雑徭が義務化された）としている。