Policies must be evaluated, and frequently policies must be changed. But neither task is as easy as some politicians, and even some academicians, make it appear. Identifying the goals of policies, determining the results of programs, and isolating the effects of policies from the effects of other social and economic forces all make evaluating public policies tricky and at times impossible. The surrogate measures that must frequently be used may be worse than no measures at all, for they emphasize activity of any sort rather than actions performed well and efficiently, placing pressure on agencies merely to spend their money rather than always to spend it wisely.

        Evaluation frequently leads to policy change, and the process of producing desired changes and implementing them in a complex political environment will tax the abilities of the analyst as well as the politician. All the usual steps in policymaking must be gone through, but they must be gone through in the presence of established organizations and clients. The implications of proposed policy changes may be all too obvious to those actors, and they may therefore resist strenuously. As often as not, the entrenched forces will be successful in deflecting pressures for change. Without the application of significant and skillful political force, then, the U.S. government often is a great machine that simply proceeds onward in its established direction. Those whose interests are already being served benefit from this inertia, but those on the outside may continue to be excluded.