Evidence-based policy: What sort of evidence do governments need?

Very few would dispute the proposition that evidence about the effects of different policy options should inform policy decisions. However, there is less agreement on the nature of the evidence needed. In addition, there may be problems in evaluating that evidence. This is particularly the case when experts offer conflicting advice. This article presents the position held by Professor Nevile that in giving policy advice to the government, it is almost always desirable to draw on a range of different policy instruments. While theoretical input is usually important, it is even more important that theory does not lose contact with the real world. Factual descriptions of the real world and the use of a theoretical toolkit containing more than one theory are essential in achieving this goal. These principles are illustrated by a discussion of a particular category of policy advice - the evaluation of government programmes.