This study concerns cooperative principles for agricultural cooperatives in Western economies. Cooperatives are to support the economic interests of their members. Cooperative principles make it possible to align members’ conflicting individual interests, thus supporting the membership’s collective interests. “Traditional cooperative principles” have historically resulted in lower average processing costs. However, in recent decades, many cooperatives have found that these principles do not provide access to adequate financial capital and qualified leaderships. Thus, some cooperatives now follow “proportional principles,” implying proportionality between members’ patronage and benefits, governance, and financing. Furthermore, “contemporary principles” allow external equity capital and professional management.