eprintid: 1553042
rev_number: 29
eprint_status: archive
userid: 608
dir: disk0/01/55/30/42
datestamp: 2017-04-22 23:55:52
lastmod: 2021-12-02 23:19:37
status_changed: 2017-08-03 10:07:02
type: article
metadata_visibility: show
creators_name: Pennington, M
creators_name: Gomes, M
creators_name: Donaldson, C
title: Handling Protest Responses in Contingent Valuation Surveys
ispublished: pub
divisions: UCL
divisions: B02
divisions: D12
divisions: G21
keywords: EuroVaQ, Heckman selection, contingent valuation, missing data, multiple imputation
note: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
abstract: OBJECTIVES: Protest responses, whereby respondents refuse to state the value they place on the health gain, are commonly encountered in contingent valuation (CV) studies, and they tend to be excluded from analyses. Such an approach will be biased if protesters differ from non-protesters on characteristics that predict their responses. The Heckman selection model has been commonly used to adjust for protesters, but its underlying assumptions may be implausible in this context. We present a multiple imputation (MI) approach to appropriately address protest responses in CV studies, and compare it with the Heckman selection model. METHODS: This study exploits data from the multinational EuroVaQ study, which surveyed respondents' willingness-to-pay (WTP) for a Quality Adjusted Life Year (QALY). Here, our simulation study assesses the relative performance of MI and Heckman selection models across different realistic settings grounded in the EuroVaQ study, including scenarios with different proportions of missing data and non-response mechanisms. We then illustrate the methods in the EuroVaQ study for estimating mean WTP for a QALY gain. RESULTS: We find that MI provides lower bias and mean squared error compared with the Heckman approach across all considered scenarios. The simulations suggest that the Heckman approach can lead to considerable underestimation or overestimation of mean WTP due to violations in the normality assumption, even after log-transforming the WTP responses. The case study illustrates that protesters are associated with a lower mean WTP for a QALY gain compared with non-protesters, but that the results differ according to method for handling protesters. CONCLUSIONS: MI is an appropriate method for addressing protest responses in CV studies.
date: 2017-02-15
date_type: published
official_url: http://doi.org/10.1177/0272989X17691771
oa_status: green
full_text_type: other
language: eng
primo: open
primo_central: open_green
article_type_text: Journal Article
verified: verified_manual
elements_id: 1288747
doi: 10.1177/0272989X17691771
lyricists_name: Gomes, Manuel
lyricists_id: MADEO09
actors_name: Gomes, Manuel
actors_name: Stacey, Thomas
actors_id: MADEO09
actors_id: TSSTA20
actors_role: owner
actors_role: impersonator
full_text_status: public
publication: Medical Decision Making
volume: 37
number: 6
pagerange: 623-634
event_location: United States
issn: 1552-681X
citation:        Pennington, M;    Gomes, M;    Donaldson, C;      (2017)    Handling Protest Responses in Contingent Valuation Surveys.                   Medical Decision Making , 37  (6)   pp. 623-634.    10.1177/0272989X17691771 <https://doi.org/10.1177/0272989X17691771>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/1553042/1/Gomes-M_handling%20protest%20responses_.pdf