Building on the term oligarchy, a system in which many are ruled by a few, sociologist Robert Michels (1876–1936) coined the term the iron law of oligarchy to refer to how organizations come to be dominated by a small, self-perpetuating elite. Most members of voluntary associations are passive, and an elite inner circle keeps itself in power by passing the leadership positions among its members.
People are excluded from leadership because they don't represent the inner circle's values—or, in some instances, their background. This is true even of organizations that are committed to democratic principles. The iron law of oligarchy is not without its limitations, of course.
Members of the inner circle must remain attuned to the opinions of the rank-and-file members, regard- less of their personal feelings. If the oligarchy gets too far out of line, it runs the risk of a grassroots rebellion that would throw the elite out of office.
This threat often softens the iron law of oligarchy by making the leadership responsive to the membership. In addition, because not all organizations become captive to an elite, the iron law of oligarchy is not really iron; it is a strong tendency, not inevitability.