Performance measures must be carefully specified so that they truly measure the performance of accountable entities rather than other changes in a community's health. If the results are to be interpreted with confidence, careful development and testing are needed to ensure that the objectives are operationalized in a clear and unambiguous way. For the HEDIS (Health Plan Employer Data and Information Set) measures, for instance, substantial time and effort was required to develop precise definitions that make sense in a variety of managed care settings and are obtainable from readily available data files (NCQA, 1993). Even a measure that seems simple, such as the proportion of children at age 24 months who have received all of the recommended immunizations, requires agreement on which immunizations are recommended at what time, decisions about whether to include children who have not been covered by the health plan since birth, and so on.
Performance measures must be written in a statistically operational form. When they are not, it can be difficult to tell what progress is being made, even if all of the information is in hand. For example, Healthy People 2000 Objective 7.17 calls for local jurisdictions to have "coordinated, comprehensive violence prevention programs." Although a long list of attributes of coordinated and comprehensive programs is given in the text, no operational definition is provided by which to judge whether a particular jurisdiction's program is coordinated and comprehensive. It would be better to identify a small number of performance indicators connecting accountable entities to specific actions, as illustrated in the committee's prototype violence indicator set (Appendix A).
Problems of this sort often arise when one does not distinguish between general health issues and operational measures of these issues. Rarely are data available in the precise form policymakers prefer, so concessions must be made to data constraints. The presentation of the performance measures should reflect this compromise by separately identifying the issues to be monitored and the best available data or proxy variables for those issues and by stating targets in terms of the measurable quantities. For example, Healthy People 2000 measures the initiation of cigarette smoking by children and youth as the proportion of cigarette smokers in the 20–24 age group. The actual measure is smoking prevalence, not initiation. This is appropriate, however, because prevalence rates are easier to obtain from population surveys and