Probability Perceptions and Preventive Health Care

We study the effect of perceptions in comparison with more objective measures of risk on individuals' decisions to decline or accept risk reducing interventions such as flu shots, mammograms, and aspirin for the prevention of heart disease. In particular, we elicit individuals' subjective probabilities of risk, with and without the interventions, and compare these perceptions to individually predicted risk based on epidemiological models. Respondents, especially women, appear to be aware of some of the qualitative relationships between risk factors and probabilities. However, on average they have very poor perceptions of the absolute probability levels as reported in the epidemiological literature. Perceptions of the level of risk are less accurate if a respondent is female and has poor numeracy skills. We find that perceived probabilities significantly affect the subsequent take-up rate of flu shots, mammograms, and aspirin, even after controlling for individually predicted risk using epidemiological models.