westward expansion, growth of corporate power, industrialization, and low commodity

 prices (Nownes & Neeley, 1996).

 Robert Salisbury theorizes that group survival depends upon an exchange of

 benefits that is mutually advantageous between the organization and the members

 (Nownes & Neeley, 1996). Salisbury's view is that people join political interest groups

 during periods of prosperity when the cost of dues is relatively painless, and that when

 times get rougher membership in organizations is one of the first cost-cutting measures in

 which people engage (Brown, 1989).

 Hansen (1985) theorized that people in different contexts have different resources

 and preferences, which indicates that they have different subjective weightings of the

 benefits and costs of participating in a group. When resources such as time and income

 are ample, people can easily bear the costs of participation. When people have particular

 needs and preferences, they are attracted to certain benefits. When people have different

 attitudes toward risk, they are more or less willing to engage in actions whose success is

 uncertain.

 An individual will join an interest group if the subjective costs incurred by joining

 are less than the subjective benefits received from membership. As the information,

 resources, preferences, and risk attitudes change in making the assessments to join, the

 attractiveness of group affiliation changes too (Hansen, 1995).

 Individuals are more easily mobilized in response to a threat than they are in

response to a prospect. The collective benefits of group membership are increased with

the awareness of threats. The effects of costs and benefits on group membership depend