Evaluation has varied roots: it is not a unified practice or derived from a single set of traditions. This is in part the result of the historical evolution of evaluation, both in Europe and in North America. As already noted, it is common to highlight three important sources of evaluation thinking. The 1960s Great Society initiatives in the United States; educational innovation and in particular curriculum innovation in schools; and budgetary control and efficiency systems such as Planning, Programming and Budgetary Systems (PPBS). In reality these are only three particular sources and one could add management by objectives, participative research in community and rural development, results based management and many more.
One way of distinguishing some of these different origins is to stand back from particular examples and look at the core ideas or theories that lie behind these different evaluation traditions.
We can distinguish between four main sets of ideas:
Scientific research and methods. Many of the basic ideas and methods used in evaluation are shared with the wider research community especially in the social sciences and economics. Within the logic that combines hypotheses testing, observation, data collection and data analysis, explanations are sought for what is observed. In complex socio-economic programmes explanations are rarely straightforward. Much of the work of evaluators is an attempt to attribute observed outcomes with known inputs and vice versa.
Economic theory and public choices. Economic thinking is present within evaluation at several different levels. These include notions of efficiency and resource allocation in the face of scarcity; institutional (mainly micro-economic) incentives and behaviours; and macro-economic studies that seek to identify aggregate effects (e.g., in terms of GDP or competitiveness) of policy interventions.
Organisation and management theory. This has begun to feature more prominently in evaluation in recent years as the focus has shifted increasingly to implementation and delivery of programmes and policies. This body of thinking highlights issues of organisational design, inter-organisational co-ordination (e.g., through partnerships and consortia), and issues of motivation, ownership and participation.
Political and administrative sciences. As public programmes and their managers address issues of the policy process and public sector reform they have increasingly drawn on ideas concerned with governance, accountability and citizenship. Many of the core ideas in public sector reform and the new public management such as transparency and accountability have been influenced by these perspectives. In addition, contemporary political perspectives highlights the importance of consensus building in order to strengthen legitimacy of policy action.
It follows from the above that evaluators are similarly diverse. They may be economists concerned with efficiency and costs; or management consultants interested in the smooth running of the organisation; policy analysts with a commitment to public sector reform and transparency; or scientists (of various disciplines) concerned to establish truth, generate new knowledge and confirm/disconfirm hypotheses.
One of the biggest problems that those who manage or commission evaluation face is how to put together a suitable team or mix of competencies that may properly come from all these traditions (this is taken further in The designing and implementing section of the GUIDE when we discuss the profile of the evaluation team and choosing the right evaluators).
At a systemic level (e.g., nationally or in Europe as a whole) one of the key tasks of evaluation capacity building is to build bridges between these different parts of the professional evaluation communities. Conferences, networks and professional societies that bring evaluators together are a way of increasing familiarity between those who come from different traditions as well as a way of transferring and sharing know-how, knowledge and expertise.
Despite these differences in evaluation origins and traditions it is possible to distinguish some of the main types of evaluation. These tend to cohere around two main axes. The first axis is about evaluation purposes and the second concerns evaluation methodologies.