tentially effective treatments will not be used if they conflict with the beliefs, cultural values, or expectations of large numbers of patients in a practice.

• Opinions of professional peers. In an environment in which it is impossible to keep up with all new advances in treatment, the opinions and practices of respected colleagues are a kind of evidence of treatment effectiveness that is often dominant.

• Reimbursement policies affecting a new treatment. Even when all other criteria have been met, a new treatment may not be adopted if the provision of it will not be adequately reimbursed.

• The extent to which the patient population is similar to those studied in clinical trials or other studies of treatment effectiveness. There are always variations in published studies of treatment effectiveness, and clinicians may legitimately believe that what works for many or most patients will not necessarily work for their own patients, particularly if they share some clinically relevant characteristic (Park, 2002).

Those who pay for health care through insurance care about effectiveness, but also about cost-effectiveness, since they have at least some responsibility to use the dollars available for insurance to produce the best possible health benefit for covered employees. Evidence of treatment effectiveness relevant to employers and insurers, then, includes

• The scientific evidence listed above for researchers.

• The preferences, expectations, and experiences of employees and their families. Employers are not insuring passive and uninformed people. Employees who have positive experiences with specific therapies will ask for such therapies to be covered by insurance plans and may use coverage for those therapies as the basis for choosing one plan over another at open enrollment or even changing jobs.

• Published cost-effectiveness studies (when available). Employers and insurers may legitimately refuse to cover treatments that are effective but that are so costly that their inclusion prevents the coverage of less costly treatments that provide more health benefit to larger numbers of people.

• Internal cost-effectiveness analyses (for some larger employers). Large companies with many thousands of employees may be able to use their own databases to study relationships between treatments and work attendance, productivity, or the costs of illness. This information may be more compelling than information in published studies because there is no question about the generalizability of the findings to that employer’s population.