CDC produces a biennial report in collaboration with state oral health and drinking water programs. Details of the calculation of fluoridation statistics are available from CDC. Recommendations for the optimal concentration of fluoride in drinking water have been published by CDC. However, water fluoridation is a state activity, and water systems apply the definition of optimal concentration determined by the state in which they operate. A description of the protocol used to characterize a community as optimally fluoridated has been published by NCHS.