Other political scientists and economists (such as Salisbury (1969), Moe (1980),

and Hansen (1985) believe that nonmaterial selective benefits and other factors

(perceptions and efficacy) explain membership in political interest groups (Brown, 1989).

The key to group formation and survival is the presence of selective benefits. These

benefits are offered to only members of the group and can include: discounts,

publications, and cheap insurance. The AFBF offers inexpensive insurance, which is a

major inducement to join, even if an individual does not agree with the Farm Bureau's

goals (Loomis & Cigler, 1995). The following services have been supplied as selective

material benefits to Farm Bureau members: (1) wide variety of insurance programs, (2)

regional and state purchasing cooperatives, (3) cooperative marketing programs, and (4)

discounts on consumer goods (Brown, 1989).

 Another area of controversy is the impact of economic conditions on political

 interest group membership. Truman's theory suggests that during hard economic times

 individuals will join organizations that work for improvement of their economic

 conditions. Truman theorized that two interrelated processes lead to group formation,

 societal change and disturbances. As society evolves and becomes more complex, new

 interest groups will emerge. Individuals are affected by "disturbances" which drive them

 to then support group endeavors. Examples of this can be found in the history of the

 formation of the major farm groups in the United States, such as the NGOPH, the

 Farmers Alliance, the AFBF, and the NFU which all emerged between 1867 and 1900.

 They were formed from an increased interaction of farmers in response to disturbances of

 their accustomed behavior. These disturbances included: technological change,