McCarthy and Zald distinguish between SM and social movement organization (SMO), or preference for change and organized action for change. A social movement is ‘a set of opinions and beliefs in a population which represents preferences for changing some elements of the social structure and/or reward distribution of a society’ (McCarthy and Zald, 1977b: 1217–18). A social movement organization is the ‘complex, or formal organization which identifies its goals with the preferences of a social movement . . . and attempts to implement these goals’ (1218). They suggest that SMs are never ‘fully’ mobilized, because those holding opinions and beliefs favouring change will always outnumber those who participate in SM activities and SMOs. They argue that, in most cases, formal or complex SMOs will become the carriers of SMs, as informal networks (so essential in the formative stages) cannot co-ordinate the complex challenges facing SMs after their emergence. Thus the task of determining the movement’s goals and program, strategy and tactics, will tend to be carried out by formal SMOs.