The last institutional isomorphism mechanism is normative isomorphism. DiMaggio and Powel viewed it as a result of professionalism involving two processes. First, members of a profession receive similar training, which socializes them into similar worldviews. Second, members of a profession interact through professional and trade associations,
which further diffuse ideas among them. Normative isomorphism corresponds to internalization of norms, but also societal pressures by members of other organizations, which imply at least some degree of external coerciveness (Perrow, 1986).
Here is a weakness of the DiMaggio and Powel framework. As pointed out by DiMaggio and Powel themselves: ‘‘this typology is an analytic one: the types are not always empirically distinct’’ (1983: 50). Mizruchi and Fein stressed the ambiguity of the various institutional isomorphism mechanisms (1999). For example, Rosenzweig and Singh noted that legal
framework is a strong environment pressure for subsidiaries of multinationals and could be described
as a coercive pressure for isomorphism (1991). However, a legal framework is also a norm and could be used to proxy normative isomorphism. This reflects an inherent ambiguity in the DiMaggio and Powel thesis, an ambiguity they recognized by noting that the three forms of institutional isomorphism are to be considered ‘‘ideal-types’’. Due to the
ambiguity of the normative isomorphism, we have not specified a hypothesis for this isomorphism.