Measuring Public Return: A Counterfactual Framework for Public ROI

Public programmes routinely claim to deliver value, yet the return on the resources they consume is rarely measured as a defined, comparable, and counterfactually attributable quantity. Two problems recur: observed public value is reported without estimating attribution, and monetization either stops too early or extends too far by assigning fragile prices to outcomes such as legitimacy or trust. This paper proposes Public ROI as a counterfactual framework for assessing public return. The framework separates attributable monetized public value and incremental full cost from three related return measures: a public benefit-cost ratio, monetized Public ROI, and net monetized public return. Non-monetized outcomes are tracked in parallel rather than forced into the monetary ratio. Attributable value is estimated against comparable control territories using a difference-in-differences design; costs are measured incrementally against the relevant counterfactual and include administrative and participant time where material. A worked example demonstrates the full computation from baseline and follow-up values to attributable return. The paper positions Public ROI relative to cost-benefit analysis, social return on investment, public-value theory, and programme evaluation, specifies measurement instruments and a validation strategy, and, for participatory-governance applications, treats engagement and democratic competence as upstream mechanisms to be tested rather than assumed. The contribution is a disciplined and auditable way to ask whether a public intervention generated value beyond what would otherwise have occurred, and whether that attributable value justified its incremental cost.