A Systematic Review and Meta-Analysis of Willingness to Pay (WTP) for Malaria Prevention and Treatment in Endemic Areas

Rationale: Predictions of the demand for, or perceived benefits of, health interventions tend to be made from the results of a single study. This has prompted researchers to explore alternative approaches to derive parameter estimates. The increasing use of WTP in malaria control interventions offers an opportunity to explore such methods and findings for a relatively similarly defined set of interventions. Objectives: To review the evidence on the willingness to pay (WTP) for malaria prevention and treatment in endemic areas, to determine what has been studied and how, provide a summary mean WTP by type of intervention, consider how and why WTP estimates vary, and advise on future reporting of WTP studies. Methodology: A systematic search of five online databases was undertaken between October 1993 and December 2005. Papers meeting inclusion criteria were double-reviewed to extract data on: context; study question and design; type of good/service valued; sampling and characteristics of sample; statistical distribution of WTP; methods of analysing WTP, and; strengths/weaknesses. Summary measures of WTP (Int$ 2006) were produced using random effects meta-analysis and compared across intervention type, elicitation format and location. Further data was collected to facilitate a random effects meta regression to examine the impact of the studies' and respondents' characteristics on WTP. Results: 33 papers from 22 studies provided 86 estimates of mean WTP. Descriptive analysis showed that 56% estimates were from Nigeria and 6% from outside Africa. 63% estimates emanated from highly or holoendemic regions and most studies used a bidding format to elicit WTP. Mean WTP varied by type of good, location and methods of analysis. Analysis using a meta-regression has highlighted the significance of national income in explaining variation. Conclusions: Meta-analysis of WTP for malaria prevention and treatment can help to compare results using different elicitation methods and facilitate the transfer of data across space and time. In practice, this analysis has shortcomings that may limit the validity of results such as the lack of specified information in some studies. However, the analysis also suggests ways in which future reporting and analysis of individual WTP studies could improve the validity and usefulness of WTP data as well as informing methods for benefit transfer method in the future