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Title: Using choice experiments to value the social benefits from reduced pesticide usage in the United Kingdom
Author: Chalak, Ali
ISNI:       0000 0001 3526 0660
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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In this thesis, a Choice Experiment (CE) approach was used to estimate public 'willingness-to-pay' (WTP) for pesticide reduction in the UK. The need to determine WTP for pesticide reductions is driven by policy pressures to reduce the associated negative externalities of pesticide use. Two surveys were undertaken to examine different aspects of this policy concern. The first survey used a CE to value the public's WTP for pesticide-free food. This survey was large in scale but relatively simple in design. The second survey employed two related but separate CEs to value WTP for reductions in insecticides, herbicides and fungicides in the UK. In particular, it was designed to examine WTP with respect to 'environmental safety' and 'food safety' issues. The first survey was part of a large survey conducted 'in-home' by MORI for DEFRA. Though access to the MORI survey yielded a large number of respondents, the simplicity of the CE is a reflection of the space constraint faced. WTP for pesticide reduction was estimated by employing a 'standard' conditional logit (CL) model. An important component of this research is the use of a novel statistical approach to generate the CL to allow and measure respondents' tendency to mis-report their 'true' preferences. To facilitate estimation, Bayesian methods were used. The motivation for employing the generalised CL lies with the considerable concern expressed in the WTP literature regarding upwardly biased WTP estimates. Bayesian factors were used to assess model specification and indicate a strong preference for the generalised CL. As anticipated, many respondents (41%) reported 'false' preferences, most of which (79%) reported in favour of 'No Pesticides' food. By accounting for bias in responses, WTP estimates were downwardly revised by 35% relative to the standard CL. However, adjusting for mis-reporting reduced WTP from 149010 to only 97% for 'No Pesticides' food. The second survey was mail-delivered and included two CEs. Though a smaller sample than the first survey was obtained, both of these CEs were much more sophisticated. These CEs differentiated environmental and health concerns, by associating each with a particular commodity: bread, and a basket of fruit and vegetables, respectively. Both CEs were designed to estimate marginal WTP for insecticide, herbicide and fungicide reductions. Using Classical statistical methods, the CL specifications revealed that being female, environment- or food safety-sensitive, living as a couple, caring for dependents, and regularly purchasing organic food are factors that increase WTP for reduced-pesticide food. However, higher income, age and education seem to reduce WTP. In order to account for heterogeneity, a latent CL model (LCM) was estimated. Segments with positive payment parameters were initially observed. 111 instance of yea-saying was resolved by discarding respondents who only chose 'No Pesticides'. The LCM revealed a significant segmentation of the population in both CEs. Moreover, the LCMs yielded higher WTP estimates than CLs. WTP, expressed as percentage or the baseline price, was higher in the 'environmental safety' CE (102% and 83% for LCM and CL respectively) than in the 'food safety' CE (69% and 40% for LCM and CL respectively). Overall, the results presented in this thesis indicate that the public is willing to pay a considerable premium for food produced using less or no pesticides. Our results are reasonably similar for the two surveys conducted and the variation in econometric methods employed. Furthermore, the results are in keeping with the limited results available in the literature to date.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available