Due to differences in ownership structure between cooperative and non-cooperative firms (NCFs), it has been hypothesized that co-ops may be less efficient than their non-cooperative counterparts. Illiquidity of owners’ investment and democratic governance may lead to underinvestment and managerial shirking in cooperative firms, both technical inefficiency sources, and the lack of a clear profit motive generates “inefficient” (relative to a profit-maximizing firm) economic decisions. This is especially true in the dairy product manufacturing sector, where production is capital intensive and factors leading to non-optimal investment decisions may have a large impact on efficiency. In this research we will use a unique dataset that includes plant level panel data for dairy product manufacturers from the Census of Manufactures encompassing the years 1977-2007 to determine whether there is a difference in plant level efficiency between cooperative firms and NCFs, as well as the source of any measured inefficiency. We will employ Data Envelopment and Stochastic Frontier (SFA) analyses to ensure robustness of results across alternative methodologies for productivity measurement.