Theory-Based Impact Evaluation

Theory-based impact evaluation evaluates a programme by first making explicit the theory of change — the causal chain of assumptions and mechanisms through which inputs are expected to produce outcomes and impacts — and then gathering evidence to test whether each link in that chain holds. Rather than treating the programme as a black box and estimating only the net effect, it asks not just whether a programme worked but why, for whom, and under what conditions. Articulated by Carol Weiss and brought into development practice by Howard White and 3ie, it complements, rather than competes with, counterfactual designs.