California, which just last year became the nation's leading dairy state, likely owes its success in that industry to the efficiency of its dairies rather than to its unique dairy marketing order, according to Daniel A. Sumner, a UC Davis professor of agricultural economics. While most of the nation's milk producers are governed by federal marketing orders -- economic regulations controlling the marketing of commodities -- California milk producers operate under a state marketing order that includes a provision for a dairy quota. The quota does not limit output, but does affect the prices paid to farmers. Milk producers in other states have charged that the California marketing order results in excess milk production. After studying the state's complicated set of economic regulations, Sumner and graduate student Christopher Wolf found that, on the contrary, California likely produces 5 to 6 percent less milk than it would without the quota. The state's abundant milk production is due to industry efficiency, not to the marketing order, they conclude.