Negative Anecdotes Reduce Policy Support: Evidence from Three Experimental Studies on Communicating Policy (In)Effectiveness

Public support is crucial for the success of policy interventions that aim to change behaviour. While communicating evidence of policy effectiveness can increase support, it remains unclear which type of evidence is most effective. Statistical evidence is often seen as objective and persuasive, yet personal anecdotes can strongly influence beliefs. We examined how statistical and anecdotal evidence affect policy perceptions. In three online experiments with representative UK samples (N = 901), we showed participants different types of evidence (statistical, anecdotal, or both) that argued for or against six policies, such as meat taxes (climate change), banning e-cigarettes (public health), and 20 mph speed limits (community safety). We measured policy support and perceived effectiveness before and after exposure and explored participants’ reasoning through open-text responses. Results showed that positive statistical and anecdotal evidence did not significantly increase perceived policy effectiveness or support, even when combined. However, negative anecdotes significantly reduced both, though this effect was sometimes mitigated when paired with statistical evidence. Qualitative results found that participants have broader concerns beyond policy effectiveness, such as fairness. Our findings suggest that communicating evidence on policy effectiveness alone may not increase support, as it does not address broader public concerns.