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Development Finance Institutions (DFIs) are frequently asked to demonstrate their additionality—meaning that they make investments that the private sector would not—but what evidence of additionality would look like is rarely articulated. This paper examines potential quantitative and qualitative evidence. We investigate whether it is possible to infer additionality from observational investment data, and show how the demand-led nature of DFIs’ business model can create bias in standard statistical techniques used to identify causal effects. Having established that rigorous evidence of additionality may continue to elude us, we discuss circumstantial evidence that would increase confidence that additionality is present, and propose a probabilistic approach to additionality.
The replication files for this paper are available for download here (.zip file).