However, as disparity of positions within government officials became wider and government officials became to be supplied from certain clans by heredity, not by meritocracy as intended by the ritsuryo system, roles of government officials became to be determined by the family lines to which they belonged and role of each family line became specialized.
しかし官人層内部での地位格差が広がり、律令体制が本来意図していた能力主義とは異質に、特定の氏族から世襲的に官人が供給されるようになると、官人の役割をその属する家系ごとに措定するようになり、家系ごとの専門化がすすんだ。