China's multi-level social security system still faces deficiencies, particularly in terms of supplementary social security in which voluntary participation remains low. Huimin Insurance, government-guided and market-operated inclusive health insurance, has grown rapidly but suffers from low enrollment rates, creating a dilemma of a “good reputation but poor sales.” To address this, this study applies Nudge theory, focusing on the core concepts of behavioral public administration “bounded rationality” and “social preference”, to examine how informational frames affect citizens' willingness to participate in Huimin Insurance. Drawing on prospect theory, risk perception and perceived value are selected as mediating variables. Two informational frames are designed: a personal risk frame highlighting individual exposure to severe disease risks and costs, and a social welfare frame emphasizing the quasi-public nature of Huimin Insurance and altruistic contributions. Two survey experiments were conducted in Liaoning province in 2023 and 2024, with 1,253 valid responses, using Huimin Insurance products with moderate versus stricter claim conditions. The results show that both frames enhance willingness under moderate conditions, with significant mediation of risk perception and perceived value. Under stricter claim conditions, however, the personal risk frame loses its direct effect and the value-based pathway disappears, indicating that participants were unwilling to perceive strict high-deductible products as valuable despite heightened risk awareness. In contrast, the social welfare frame demonstrates robust effects across both experiments, enhancing willingness both directly and indirectly through either mediator. Quantitatively, in the moderate condition, indirect effects of risk perception and perceived value accounted for 11.8 percent and 32.4 percent, respectively, of the total effect for the personal risk frame, and 10.5 percent and 37.2 percent, respectively, for the social welfare frame. In the stricter condition, risk perception explained nearly 75 percent of the personal risk frame's total effect, while perceived value was insignificant, showing the sensitivity of risk-based nudges to product design. Meanwhile, the social welfare frame maintained balanced mediation, with risk perception and perceived value accounting for 21.1 percent and 44.4 percent of the total effect, underscoring the stable impact of altruism-oriented framing. Sensitivity analysis confirmed the robustness of these mediation pathways, as substantial unobserved confounding would be required to overturn the results. Theoretically, the study extends Nudge theory to China's supplementary social security, enriches applications of prospect theory, and advances behavioral public administration by revealing distinct mechanisms of risk-based versus altruism-based framing. It also demonstrates that claim conditions interact with informational frames, shaping the extent to which psychological drivers can be activated. Practically, the study suggests strengthening risk communications and health education, highlighting the robust effectiveness of social welfare framing to motivate participation, and enhancing transparency and regulation to maintain the public welfare orientation of Huimin Insurance. Public campaigns, combining government credibility, professional expertise, and community engagement, can further embed Huimin Insurance as a mutual-aid initiative. Furthermore, establishing clear oversight, auditing, and feedback mechanisms is essential to sustain trust among healthy participants and to safeguard the program's quasi-public identity. In conclusion, informational frames serve as effective nudges for promoting supplementary social security participation in China, with social welfare framing proving consistently influential even under unfavorable product conditions.
WANG et al. (Mon,) studied this question.