When “once or twice” does not count: rethinking bullying measurement in the <i>Health Behaviour in School-aged Children</i> study

Bullying represents a major public health concern worldwide. Large-scale, cross-national surveys play a key role in estimating its prevalence and informing prevention policies. However, specific operational decisions may systematically bias these estimates. In particular, the Health Behaviour in School-aged Children (HBSC) study has monitored in-school bullying since the early 1990s. In most HBSC publications, participants reporting having bullied or been bullied ‘once or twice in the past couple of months’ are excluded from analyses. This practice leads to the underestimation of bullying prevalence, misclassification of perpetrators and victims, and potentially distorted associations with psychosocial correlates. The exclusion is seldom justified and, when it is, rests on unsound methodological and theoretical foundations. I therefore recommend including all self-reported bullies and victims to improve profiling accuracy and, by extension, the effectiveness of prevention efforts.