Bridging the gap between self-assessments and measured household food waste: A hybrid valuation approach

Great effort is invested in mapping the extent of household food waste and its main determinants. However, food waste valuation remains a challenging task. Valuation methods can be divided roughly into objective measurements that are based on physical waste surveys, and subjective self-assessments that are based on diaries or questionnaires. Self-assessment methods have been more popular than food waste measurement because they are less costly. The goal of this paper is to empirically test whether self-assessments can accurately reflect objective measurement. To answer this question, we implemented a hybrid valuation approach by integrating and comparing three methods: a self-assessment questionnaire, a physical waste survey, and a food expenditure survey. Self-assessments slightly underestimated measured food waste proportion (13.7% vs. 16.3%, respectively). The results also show a positive, yet, not very strong correlation between the measures and the self-assessments of unconsumed and partly consumed avoidable food waste in most food categories. Self-assessments of monetary losses were €42.07 per household per month on average, overestimating calculated losses of €25.74 on average. Our findings question the validity of self-assessments. The current paper demonstrates the questionable nature of the implicit assumption that self-assessment reflects the true level of food waste and suggests a rigorous method for exploring this relation.