Estimating the economic benefits of avoiding food-borne risk: is 'willingness to pay' feasible?

Annual cost of illness and quality-adjusted life year losses in the United States due to 14 foodborne pathogens

In this article we estimate the annual cost of illness and quality-adjusted life year (QALY) loss in the United States caused by 14 of the 31 major foodborne pathogens reported on by Scallan et al. (Emerg. Infect. Dis. 17:7-15, 2011), based on their incidence estimates of foodborne illness in the United States. These 14 pathogens account for 95 % of illnesses and hospitalizations and 98 % of deaths due to identifiable pathogens estimated by Scallan et al. We estimate that these 14 pathogens cause $14.0 billion (ranging from $4.4 billion to $33.0 billion) in cost of illness and a loss of 61,000 QALYs (ranging from 19,000 to 145,000 QALYs) per year. Roughly 90 % of this loss is caused by five pathogens: nontyphoidal Salmonella enterica ($3.3 billion; 17,000 QALYs), Campylobacter spp. ($1.7 billion; 13,300 QALYs), Listeria monocytogenes ($2.6 billion; 9,400 QALYs), Toxoplasma gondii ($3 billion; 11,000 QALYs), and norovirus ($2 billion; 5,000 QALYs). A companion article attributes losses estimated in this study to the consumption of specific categories of foods. To arrive at these estimates, for each pathogen we create disease outcome trees that characterize the symptoms, severities, durations, outcomes, and likelihoods of health states associated with that pathogen. We then estimate the cost of illness (medical costs, productivity loss, and valuation of premature mortality) for each pathogen. We also estimate QALY loss for each health state associated with a given pathogen, using the EuroQol 5D scale. Construction of disease outcome trees, outcome-specific cost of illness, and EuroQol 5D scoring are described in greater detail in a second companion article.

Aggregation rules for cost-benefit analysis: a health economics perspective

Few willingness-to-pay (WTP) studies in the health sector have used their results within a cost-benefit analysis (CBA), an essential step to informing resource allocation decisions. This paper provides an overview of aggregation methods, reviews current evidence of practice in the health sector, and presents estimates of the total economic value of a women's group programme to improve mother and newborn health using different aggregation rules. A contingent valuation survey was conducted with 93 women's group members, 70 female non-members and 33 husbands. Aggregation was conducted with and without the values of non-users, and with different units of aggregation. The unadjusted mean, median and a weighted mean transfer were used to aggregate values. Equity weights were introduced to adjust WTP for income. Total WTP more than doubled when the values of husbands were added to that of women, and increased over 10-fold when the values of women who were not members of the group were added. The inclusion of non-use values, and the unit of aggregation, had the greatest effect on results. Researchers must reach agreement on the most acceptable method of aggregating WTP values to promote the use of WTP in resource allocation decisions in the health sector.

Benefits transfer of willingness to pay estimates and functions for health-risk reductions: a cross-country study

This paper provides a first application of the techniques of benefits transfer to the health economics literature. These techniques seek to transfer the value of some good from one 'survey' context to a new 'policy' context so avoiding the need for new valuation surveys each time a new policy question arises. Two approaches to benefits transfer are assessed: the simple transfer of mean values and the transferral of value functions. We develop a new methodology for the latter approach in which value functions are iteratively built up from theoretical principles with transfer errors being tested each time a new variable is added. Through a novel application of advanced statistical tests we show that this approach outperforms the transferral of statistically driven Best-fit functions. The case study presented focuses upon the transfer of contingent valuation (CV) willingness to pay (WTP) estimates and associated value functions for reducing the health risks associated with solar ultraviolet (UV) exposure. Common format studies are conducted in four countries with transfers between all of these being undertaken. By calculating errors in predicted versus actual values across countries we show that, when transferring between similar contexts, simple mean-value transfers outperform more complex value function transfers (with the magnitude of the former errors being encouragingly small). However, this result is reversed when transfers are undertaken across dissimilar contexts where value functions partially adjust for these differences. In summary these findings provide support and guidance for future applications.

The benefit of health insurance coverage of contraceptives in a population-based sample

This study estimated the value of contraceptives, through a random-digit-dialed survey of willingness to pay for health insurance coverage of contraceptives among 659 Washington State adults. People valued contraceptives at 5 times the actuarial cost; in general, women and reproductive-aged persons were willing to pay more, but low-income men highly valued contraceptives. Most respondents (85%) said that contraceptives should be covered by health insurance plans. The full benefit of contraceptives exceeds their cost.

The contingent valuation method in health care

The contingent valuation method (CVM) is a survey-based, hypothetical and direct method to determine monetary valuations of effects of health technologies. This comprehensive review of CVM in the health care literature points at methodological as well as conceptual issues of CVM and on willingness to pay as a measure of benefits compared with other measures used in medical technology assessment. Studies published before 1998 were found by searching computerised databases and former review literature. Studies were included, when performing CVM using original data and meeting qualitative criteria. Theoretical validity of CVM was sufficiently shown and there were several indications of convergent validity. No results on criterion validity and only a few on reliability were found. There was widespread use of different elicitation formats, which make comparisons of studies problematic. Direct questions were seen problematic. First bids used in bidding games influenced the monetary valuation significantly (starting point bias). There were indications that the range of bids of payment cards also affected the valuation (range bias). However, no strategic bias was found. The influence of different states of valuation (ex-ante, ex-post) and of payment methods, as well as the possible aggregation of the results of decomposed scenarios rather than more complex holistic scenarios, were rarely investigated. Further methodological analysis and testing seems to be necessary before CVM may be used in health care decision making. Important research topics are the connection of assessment of different elicitation methods and criterion validity as well as tests on reliability according to methodological issues. Concerning conceptual issues, the analysis of the influence of different states of evaluation and of the status of the respondents as diseased or non-diseased, as well as the aggregation of results of decomposed scenarios, proved to be topics of further research.

Willingness to pay: a method for measuring preferences for maternity care?

BACKGROUND

The aim of this study was to assess the feasibility of the use of "willingness to pay" as a measure of the benefits of intrapartum care.

METHODS

A questionnaire was mailed to 150 pregnant women booking at Aberdeen Maternity Hospital in the northeast of Scotland, giving information on options for intrapartum care compiled from a recent randomized trial of care in a midwife-managed delivery unit versus care in a consultant-led labor ward. Women were asked which type of care they preferred and what would be their maximum willingness to pay for their preferred option. Data were also collected on demographic and clinical characteristics.

RESULTS

Most women (55%) expressed a preference for care in a midwives unit. However, strength of preference, as reflected in willingness to pay, was greater among those in the smaller group, who expressed a preference for care in a consultant-led labor ward. The willingness-to-pay results were not associated with ability to pay.

CONCLUSIONS

These data should be used together with cost data to decide on provision of care. Given the strength of preference of the minority group, and if the cost implications are not too great, a flexible service that takes account of women's wishes should be provided, even if this goes against the trend for care of those at low risk. By analyzing choice of care by income groups and social class groupings, it is possible to examine whether willingness-to-pay results are associated with indicators of ability to pay. In this case, they were not. Willingness to pay has an advantage in allowing respondents to account for more than just health gain when valuing different types of care.