There is a growing interest, notably in development economics, in extending project evaluation methods to the evaluation of multiple interventions (“programs”). In program evaluations one is interested in the aggregate impact of a program rather than the effect on individual beneficiaries....

Donor agencies and recipient governments want to assess the effectiveness of aid-supported sector policies. Unfortunately, existing methods for impact evaluation are designed for the evaluation of homogeneous interventions (‘projects’) where those with and without ‘treatment’ can be...