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Any Organized social group is always a stratified social body. There has not been and does not exist any permanent social group which is "flat" and in which all members are equal.

Pitirim Aleksandrovich Sorokin (1998). “Social Mobility”, p.12, Taylor & Francis
Any Organized social group is always a stratified social body. There has not been and does not exist any permanent social group which is flat and in which all members are equal.