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The stability of people’s preferences for ecosystem services over long time periods remains underexplored. We examine the dynamics of willingness to pay (WTP) to prevent coastal ecosystem damage using two identical contingent valuation surveys administered to a high-quality Norwegian panel in 2015 and 2020. The 2020 sample includes new respondents and re-testers, yielding a large test-retest sample across a five-year period. We find evidence that neither mean WTP nor underlying preferences are temporally stable. Comparing the 2015 sample to new respondents in 2020, we estimate an increase in WTP driven by heterogeneity in both respondent characteristics and preference parameters. A modest decrease in WTP is estimated for the test-retest sample, which we ascribe to shifting preferences. Investigation of respondent-level dynamics in WTP highlights potential mechanisms behind the negative preference shift. Our study highlights important factors to consider when transferring stated preferences across long time periods, and demonstrates the need for future research on how environmental preferences evolve over time. • WTP stability over 5 years is analyzed via identical contingent valuation surveys • Results from a test-retest panel reveal changes at the individual level • A negative shift in preferences is revealed among the test-retest respondents • WTP increased in independent samples due to observed and unobserved heterogeneity • Multiple potential mechanisms for the preference instability are investigated
Ørbeck et al. (2026) studied this question.