Think of a number... any number?

Stability of Willingness to Pay: Does Time and Treatment Allocation in a Randomized Controlled Trial Influence Willingness to Pay?

BACKGROUND

Willingness-to-pay (WTP) estimates are useful to policy makers only if they are generalizable beyond the moment when they are collected. To understand the "shelf life" of preference estimates, preference stability needs be tested over substantial periods of time.

METHODS

We tested the stability of WTP for preventative dental care (scale and polish) using a payment-card contingent valuation question administered to 909 randomized controlled trial participants at 4 time points: baseline (prerandomization) and at annual intervals for 3 years. Trial participants were regular attenders at National Health Service dental practices. Participants were randomly offered different frequencies (intensities) of scale polish (no scale and polish, 1 scale and polish per year, 2 scale and polishes per year). We also examined whether treatment allocation to these different treatment intensities influenced the stability of WTP. Interval regression methods were used to test for changes in WTP over time while controlling for changes in 2 determinants of WTP. Individual-level changes were also examined as well as the WTP function over time.

RESULTS

We found that at the aggregate level, mean WTP values were stable over time. The results were similar by trial arm. Individuals allocated to the arm with the highest scale and polish intensity (2 per year) had a slight increase in WTP toward the latter part of the trial. There was considerable variation at the individual level. The WTP function was stable over time.

CONCLUSIONS

The payment-card contingent valuation method can produce stable WTP values in health over time. Future research should explore the generalizability of these results in other populations, for less familiar health care services, and using alternative elicitation methods.

HIGHLIGHTS

Stated preferences are commonly used to value health care.Willingness-to-pay (WTP) estimates are useful only if they have a "shelf life."Little is known about the stability of WTP for health care.We test the stability of WTP for dental care over 3 y.Our results show that the contingent valuation method can produce stable WTP values.

"Willingness to Pay": The Value Attributed to Program Location by Pulmonary Rehabilitation Participants

The "contingent valuation" method is used to quantify the value of services not available in traditional markets, by assessing the monetary value an individual ascribes to the benefit provided by an intervention. The aim of this study was to determine preferences for home or center-based pulmonary rehabilitation for participants with chronic obstructive pulmonary disease (COPD) using the "willingness to pay" (WTP) approach, the most widely used technique to elicit strengths of individual preferences. This is a secondary analysis of a randomized controlled equivalence trial comparing center-based and home-based pulmonary rehabilitation. At their final session, participants were asked to nominate the maximum that they would be willing to pay to undertake home-based pulmonary rehabilitation in preference to a center-based program. Regression analyses were used to investigate relationships between participant features and WTP values. Data were available for 141/163 eligible study participants (mean age 69 [SD 10] years, n = 82 female). In order to undertake home-based pulmonary rehabilitation in preference to a conventional center-based program, participants were willing to pay was mean $AUD176 (SD 255) (median $83 [IQR 0 to 244]). No significant difference for WTP values was observed between groups (p = 0.98). A WTP value above zero was related to home ownership (odds ratio [OR] 2.95, p = 0.02) and worse baseline SF-36 physical component score (OR 0.94, p = 0.02). This preliminary evidence for WTP in the context of pulmonary rehabilitation indicated the need for further exploration of preferences for treatment location in people with COPD to inform new models of service delivery.

Longitudinal changes and determinants of parental willingness to pay for the prevention of childhood overweight and obesity

BACKGROUND

Willingness to Pay (WTP) is an alternative to measure quality-adjusted life years for cost-effectiveness analyses. The aim was to evaluate longitudinal changes and determinants of parental WTP for the prevention of childhood overweight and obesity.

METHODS

Longitudinal data from post- (T2) and follow-up (T3) measurements of a school-based health promotion program in Germany. Parental questionnaires included general WTP and the corresponding amount to reduce incidental childhood overweight and obesity by half. Longitudinal differences were examined with the McNemar test for general WTP and the Wilcoxon signed-rank test for the amount of WTP. Regression analyses were conducted to detect determinants.

RESULTS

General parental WTP significantly decreased from 48.9% to 35.8% (p < 0.001, n = 760). Logistic regression analysis (n = 561) showed that parents with a tertiary education level and a positive general WTP at T2, families with a higher monthly household income, and those with abdominally obese children were significant predictors of general WTP at T3. Median amount of WTP at T3 was €20.00 (mean = €27.96 ± 26.90, n = 274). Assuming a WTP of €0 for those who were generally not willing to pay or did not answer, resulted in a median amount of WTP at T3 of €0 (m = €8.45, sd = €19.58, n = 906). According to linear regression analysis WTP at T2 was the only significant predictor for the amount of WTP at T3 (p = 0.000, n = 181).

CONCLUSIONS

Despite the decline of general WTP, these results are a reflection of the public awareness of the problem and the need for action. Policy makers should recognize this and initiate sustainable public preventive strategies.

TRIAL REGISTRATION

DRKS, DRKS00000494. Registered 25 August 2010, https://www.drks.de/drks_web/.

Stubbing out hypothetical bias: improving tobacco market predictions by combining stated and revealed preference data

In health, stated preference data from discrete choice experiments (DCEs) are commonly used to estimate discrete choice models that are then used for forecasting behavioral change, often with the goal of informing policy decisions. Data from DCEs are potentially subject to hypothetical bias. In turn, forecasts may be biased, yielding substandard evidence for policymakers. Bias can enter both through the elasticities as well as through the model constants. Simple correction approaches exist (using revealed preference data) but are seemingly not widely used in health economics. We use DCE data from an experiment on smokers in the US. Real-world data are used to calibrate the scale of utility (in two ways) and the alternative-specific constants (ASCs); several innovations for calibration are proposed. We find that embedding revealed preference data in the model makes a substantial difference to the forecasts; and that how models are calibrated also makes a substantial difference.

Validity of Willingness to Pay Measures under Preference Uncertainty

Recent studies in the marketing literature developed a new method for eliciting willingness to pay (WTP) with an open-ended elicitation format: the Range-WTP method. In contrast to the traditional approach of eliciting WTP as a single value (Point-WTP), Range-WTP explicitly allows for preference uncertainty in responses. The aim of this paper is to apply Range-WTP to the domain of contingent valuation and to test for its theoretical validity and robustness in comparison to the Point-WTP. Using data from two novel large-scale surveys on the perception of solar radiation management (SRM), a little-known technique for counteracting climate change, we compare the performance of both methods in the field. In addition to the theoretical validity (i.e. the degree to which WTP values are consistent with theoretical expectations), we analyse the test-retest reliability and stability of our results over time. Our evidence suggests that the Range-WTP method clearly outperforms the Point-WTP method.

Comparing welfare estimates from payment card contingent valuation and discrete choice experiments

This study presents the first comparison of willingness to pay estimates derived from the payment card (PC) contingent valuation and discrete choice experiment (DCE) methods. A within-sample experiment was used to elicit women's preferences for Chlamydia screening. The willingness to pay estimate derived from the DCE was larger than that derived from the PC. To investigate why the willingness to pay estimates were different, a range of validity tests were conducted. Both methods produced theoretically valid results, and there was no difference in the reported difficulty of completing the tasks. Evidence of a prominence effect was found in the PC responses. Responses to the DCE satisfied tests of non-satiation. Responses to both methods were compared with revealed preference data. There were significant differences between stated screening intention in both methods and actual screening uptake. Future work should address the external validity of stated preference methods.

The role of 'reference goods' in contingent valuation: should we help respondents to 'construct' their willingness to pay?

A general population sample of 135 Australian respondents completed one of four contingent valuation surveys that asked them to value health benefits either in the absence of an explicit reference good or in the presence of one of three different forms of reference good. Results suggest that respondents have a 'ball-park' figure that is then challenged by the reference good. For values that appear far lower than, or similar to, this 'ball-park' figure, the reference good has little quantitative effect, but qualitatively appears to help respondents in their confidence in this value being their actual WTP. The implications for CV research in health care are outlined in the discussion.

Patients' willingness to pay for electronic communication with their general practitioner

Despite the common use of electronic communication in other aspects of everyday life, its use between patients and health care providers has been slow to diffuse. Possible explanations are security issues and lack of payment mechanisms. This study investigated how patients value secure electronic access to their general practitioner (GP). One hundred and ninety-nine patients were asked an open-ended willingness-to-pay (WTP) question as part of a randomised controlled trial. We compared the WTP values between two groups of respondents; one group had had the opportunity to communicate electronically with their GP for a year and the other group had not. Fifty-two percent of the total sample was willing to pay for electronic GP contact. The group of patients with access revealed a significantly lower WTP than the group without such access. Possible explanations are that the system had fewer benefits than expected, a presence of hypothetical bias or simply a preference for face-to-face encounters.