Theory-Based Impact Evaluation

Calls for rigorous impact evaluation have been accompanied by the quest not just to find out what works but why. It is widely accepted that a theory-based approach, one that maps out the causal chain from inputs to outcomes and impact and tests the underlying assumptions, will shed light on the 'why' question. But application of a theory-based approach remains weak. This paper identifies six principles to successful application of the approach:

1. map out the causal chain (programme theory);
2. understand context;
3. anticipate heterogeneity;
4. rigorously evaluate impact using a credible counterfactual;
5. conduct rigorous factual analysis; and
6. use mixed methods.