Time vs. money metrics for contingent valuation surveys: Theory and correlations from data on two marine ecosystems

Money remains the most commonly used metric in valuation surveys involving non-market goods, though recent evidence suggests that alternative metrics can be equally effective. This research contributes to the literature by (i) suggesting a theoretical model to explain the links between metrics, (ii) proposing a bivariate lognormal model to account for any correlation between the answers to the valuation questions, and (iii) providing new data on the value of preserving "blue goods" in a rural area of a developing country. We study a measure of willingness to pay (WTP) for a non-market good in a time and money metric and show that the ratio between WTP in the time/money metric is equal to the wage in a competitive economy. Our model is tested using a field survey on conservation of "blue goods" (ecosystems involving the husbandry of water resources) in rural Philippines, and the results provide further support for the use of alternative metrics in valuation studies.