The Impact of Forced Choice on Person Trade-Offs: Evidence on Age Weights for Paediatric Health Gains

Background This study examines the impact of forced versus unforced choice formats in Person Trade Off (PTO) experiments on eliciting age weights for gains in health for children and young people compared to adults. While PTOs are widely used to elicit societal preferences, the effect of including a ‘no preference’ option has not been fully investigated. Methods A randomised online survey was conducted in Australia (n=2,098), comparing two PTO arms: one forced choice and one unforced, allowing a ‘no preference’ response. Respondents evaluated five health gains (life extension and quality-of-life improvements) across 13 child/adolescent age groups versus adults aged 40 or 55. Equivalence ratios were calculated using bisection methods, and aggregate age-weights were derived using Ratio of Means (RoM) and Ratio of Geometric Means (RoGM). Consistency and cardinal transitivity were assessed, and logistic regressions were used to explore associations with respondent characteristics. Results Significant differences in age-weights were found between the unforced and forced arms. The unforced arm yielded more stable responses, with lower variance in RoM/RoGM estimates and fewer inconsistencies with attitudinal questions. Respondents in the forced arm were 1.5 times more likely to fail transitivity and 1.4 times more likely to provide inconsistent responses. The differences between forced and unforced arms were more evident in comparisons with older adults (i.e., 55 years) than with young adults (40 years). Conclusions Including a ‘no preference’ option in PTO designs improves response consistency and stability, suggesting unforced formats may better capture societal values in age weights. These findings have implications for health technology assessment and equity-sensitive priority setting.