2.12 Finally, there is the additional question of why what was observed about a policy's processes or outcomes occurred. In some limited cases, this might be of only secondary interest - so long as an intervention can be shown to work, the exact reasons why might be considered unimportant. In other cases, the particular evaluation technique adopted might not be capable of explaining the mechanisms involved. It is likely, however, that an understanding of why the policy generated the processes and outcomes it did will be desirable for a number of reasons, including:
• so that effectiveness and value for money can be improved by emphasising the most successful parts of the policy and minimising (and maybe stopping) those which work less well. The understanding can also permit any factors which are hindering policy effectiveness to be addressed, including making the policy work better for those individuals or areas who benefited less than others, and avoiding any undesirable unintended consequences;
• so that policy scope and coverage can be successfully and effectively extended (e.g. through the national roll-out of a regional pilot). Future policy-making can be informed and improved through contribution to the evidence base around "what works"; and
• an understanding of the workings of a policy and the reasons for its success adds to the credibility of accountability and value for money statements, and improves transparency and decision-making, as outlined in Chapter 1.