Contribution analysis is a 6-step process to systematically test the different stages of the theory of change of the intervention being evaluated. For each step, it indicates whether or not the expected changes have occurred, and identifies in a contribution story the main direct and indirect contributions to these changes, including the intervention being evaluated.
For example, to assess the contribution of a research centre to decision-making on a given subject, one would first identify the ways in which this centre (or others) could contribute to the decision. Then the analysis will aim first to qualify what decisions were taken and how; then look at the evidence (dis)confirming the contribution claims; at the evidence of other contributions; and finally explain these contributions.