Theory of Change is not a small n impact evaluation; rather, it is a precursor to undertaking most small n impact evaluations.

A useful Theory of Change must set out clearly the causal mechanisms by which the intervention is expected to achieve its outcomes (HM Treasury 2020). The Magenta Book (HM Treasury 2020) details how more sophisticated Theory of Change exercises produce a detailed and rigorous assessment of the intervention and its underlying assumptions, including the precise causal mechanisms that lead from one step to the next, alternative mechanisms to the same outcomes, the assumptions behind each causal step, the evidence that supports these assumptions, and how different contextual, behavioural and organisational factors may affect how, or whether, outcomes occur.

What is involved?

There is no set method for developing a Theory of Change. The process often starts with articulating the desired (long-term) change that a programme or intervention intends to achieve, based on a number of assumptions that hypothesise, project or calculate how change can be enabled. The following questions, based closely on the Early Intervention Foundation’s 10 Steps for Evaluation Success, can be used to structure the process of building a Theory of Change:

  • What is the intervention’s primary intended outcome?
  • Why is the primary outcome important and what short and long-term outcomes map to it?
  • Who is the intervention for?
  • Why is the intervention necessary?
  • Why will the intervention add value?
  • What outputs are needed to deliver the short-term outcomes?
  • What will the intervention do?
  • What inputs are required?

To be a useful starting point for a small n impact evaluation, the Theory of Change must set out clearly the causal mechanisms by which the intervention is expected to achieve its outcomes. An understanding of the causal mechanisms will develop from both engagement with key informants and an understanding of the scientific evidence base.

The development of a Theory of Change is fundamentally participatory. Evaluators should include a variety of stakeholders and, therefore, perceptions. The process of developing a Theory of Change should be based on a range of rigorous evidence, including local knowledge and experience, past programming material and social science theory. It is common to use workshops as part of the process, but document reviews, evidence reviews and one-to-one interviews with key informants are also likely to feature.
Download a Theory of Change case study here
Download a longer briefing on the Theory of Change here

Useful resources

Many organisations have produced guidance on the Theory of Change.

TASO has produced guidance on developing a Theory of Change as part of their wider evaluation guidance. This is supported by videos discussing Theory of Change and how to run a Theory of Change workshop.

Many other organisations have also produced guides. A few of these include:

Asmussen, K., Brims, L. and McBride, T. (2019) 10 steps for evaluation success, London: Early Intervention Foundation. See pp. 15–26.

Noble, J. (2019) Theory of change in ten steps, London: New Philanthropy Capital.

Rogers, P. (2014). Theory of Change, Methodological Briefs: Impact Evaluation 2, UNICEF Office of Research, Florence.

A helpful worked example of how to build a Theory of Change produced by ActKnowledge and the Aspen Institute Roundtable on Community Change is available here.