Does the messenger matter? Scenario credibility and information source in valuing health risk reductions from air pollution

Perceived realism of the policy scenario presented in stated preference (SP) valuation depends on trust in the scientific soundness of the projected policy outcomes (epistemic credibility) and in policymakers' capability to deliver them (implementation credibility). Using a discrete choice experiment (DCE) with 1,100 Polish urban residents, we examine how policy scenario credibility shapes preferences for air pollution mitigation reducing risks from chronic obstructive pulmonary disease (COPD). We contrast domain experts and artificial intelligence (AI) with no-source control as information sources on policy outcome projections. We find that epistemic and implementation credibility are strongly correlated; thus, we treat credibility as a single variable affecting preferences. Using a hybrid mixed logit (HMXL) model, we demonstrate that higher perceived credibility increases programme support, lowers cost sensitivity, and thus elevates willingness to pay (WTP) for the programme and morbidity risk reduction. We find no evidence that the information source influences preferences or scenario credibility.