Protest response and willingness to pay for culturally significant urban trees: Implications for Contingent Valuation Method

- Protest responses are zero willingness-to-pay (WTP) that is not amenable to economic theory.
- Censoring protest WTPs is a common practice in the use of Contingent Valuation Method.
- This study examined the relationship between protest belief and WTP for urban trees.
- We found both positive and negative relationships between them.
- Findings raise question about the assumptions underlying the censoring treatment.

The Contingent Valuation Method (CVM) could assist green-space planning, management and appreciation by assigning a monetary value to urban trees. However, the use of CVM is limited by its inherent methodological weaknesses. A critical concern is the existence of a large proportion of survey respondents providing zero willingness-to-pay (WTP) and that these responses are not amenable to economic theory - known as 'protest' responses. Censoring protest responses from further treatment is a common practice, which warrants reconsideration in light of our CVM survey results. The survey involved 800 residents requested to state their WTP for preserving the culturally significant stonewall trees in urban Hong Kong. About 28% of respondents returned a zero WTP. For all respondents the strength of protest beliefs was assessed, and the relationship between protest beliefs and WTP were examined. Our analysis produced contradictory results: some protest items varied negatively with WTP as expected, but other items increased with it. Respondents' stated positive WTP harbored latent protest beliefs which are related to non-economic preference. The findings stand at odds with the assumptions underlying the censoring treatment and raise questions about the validity of WTP estimates. These methodological implications should be taken into account in using CVM.