A comparison of empirical models used to infer the willingness to pay in contingent valuation

The essence of the contingent valuation method consists of creating a hypothetical market where respondents are asked about their willingness to pay (WTP) for a non-market good. Different empirical models can be formulated to estimate the expected WTP of a sample of respondents and, then, through aggregation, the social valuation of the good is inferred.This paper outlines the relevance of the distributional assumptions when estimating mean WTP. Several parametric and non-parametric methods are discussed and applied to calculate the existence value of a natural space. Results show that WTP is extremely sensitive to the empirical model used.First version received: November 2002 / Final version received: January 2004     

Asking for Individual or Household Willingness to Pay for Environmental Goods?

The aggregate welfare measure for a change in the provision of a public good derived from a contingent valuation (CV) survey will be higher if the same elicited mean willingness to pay (WTP) is added up over individuals rather than households. A trivial fact, however, once respondents are part of multi-person households, it becomes almost impossible to elicit an “uncontaminated” WTP measure that with some degree of confidence can be aggregated over one or the other response unit. The literature is mostly silent about which response unit to use in WTP questions, and in some CV studies it is even unclear which type has actually been applied. We test for differences between individual and household WTP in a novel, web-administered, split-sample CV survey asking WTP for preserving biodiversity in old-growth forests in Norway. Two samples are asked both types of questions, but in reverse order, followed by a question with an item battery trying to reveal why WTP may differ. We find in a test between samples that the WTP respondents state on behalf of their households is not significantly different from their individual WTP. However, within the same sample, household WTP is significantly higher than individual WTP; in particular if respondents are asked to state individual before household WTP. Our results suggest that using individual WTP as the response unit may overestimate aggregate WTP. Thus, the choice of response format needs to be explicitly and carefully addressed in CV questionnaire design and further research in order to avoid the risk of unprofitable projects passing the benefit-cost test.

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A field experiment to estimate the effects of anchoring and framing on residents’ willingness to purchase water runoff management technologies

Watersheds throughout the world have been severely polluted by nutrient-laden runoff that comes from industrial, agricultural, and residential sources. Efforts to reduce this runoff have focused on industrial and agricultural sources, while little attention has been paid to encouraging residents to reduce runoff from their properties. To study residents’ willingness to adopt landscaping practices that reduce runoff, we conducted a field experiment in the Delaware River watershed. In the experiment, over three hundred adults participated in a series of random-price auctions that revealed their willingness to pay (WTP) for five products that reduce nutrient runoff. To study how WTP can be influenced by attributes of the choice architecture, we randomized the starting bid values (anchors) and the way in which the external benefits of the five practices were framed. Compared to a neutral framing, a positive framing (using the product can improve water quality) increased average WTP by about one-third, while the estimated effect of a negative framing (failing to use the product can worsen water quality) was also positive, but smaller and not statistically different from zero. The estimated effect on average WTP from the anchor depends on how bids of $0 are modeled, but the results imply that higher anchors lead to higher WTP. Although we believe the magnitudes of our results should be considered suggestive and we recommend replications with higher statistical power, the results add to the evidence base that environmental programs can achieve policy-relevant gains in program performance through a series of small changes to the decision environment.     

The willingness to pay–willingness to accept gap: A failed replication of Plott and Zeiler

The well-known willingness to pay–willingness to accept (WTP–WTA) gap refers to the observation that individuals attach a higher value to objects they own (WTA) than to objects they do not own (WTP). We report on experiments to re-investigate the possibility that the WTP–WTA gap arises from subject misconceptions due to experimental procedures as suggested by Plott and Zeiler (2005). The contribution of this paper is two-fold: first, we attempt to replicate the findings by Plott and Zeiler that the WTP–WTA gap disappears when using procedures that are aimed at reducing misconceptions, such as extensive training and practice rounds for the BDM mechanism. However, we fail to do so as the WTP–WTA gap persists in the main task where subjects state their WTA or WTP for a mug. Second, we use the paid practice rounds to identify subjects without apparent misconceptions and find that also for those subjects who never make dominated choices in the lottery tasks, the WTP–WTA gap in the mug task exists. Thus, we find no evidence of the idea that subject misconceptions are the main source of the WTP–WTA gap.     

Willingness to pay for publicly-financed health care: how should we use the numbers?

This paper addresses the question of how willingness to pay (WTP) values in health care evaluation can be used by policy makers. The way in which WTP values are used depends on from whom values are elicited and whether the good concerned is privately-financed or publicly-financed through taxation. Thus, four possible uses of WTP values are identified. The focus is on the two uses which arise in the publiclyfinanced situation. ‘Conventional’ use of WTP values, where the decision as to whether or not to provide a service depends upon whether or not WTP values are greater than total cost, applies only in the privately-financed, and not publiclyfinanced situations. The situations with publicly-financed goods are more complex. The use of WTP values for publicly-financed goods is justified and illustrated.     

Tax incentives and the decision to purchase long-term care insurance

This paper studies the impact of the tax incentive prescribed in the Health Insurance Portability and Accountability Act of 1996 (HIPAA) on individuals' long-term care insurance purchasing behavior. Using data from the Health and Retirement Study, we find that the tax incentive in HIPAA increased the take-up rate of private LTC insurance by 3.3 percentage points, or 25%, for those eligible. Despite this seemingly strong response, our results imply that even an above-the-line tax deduction would not increase the coverage rate of seniors beyond 13%, indicating that tax incentives alone are unlikely to expand the market substantially. We also present, to our knowledge, the first estimate of the price elasticity of demand for LTC insurance of around ? 3.9, suggesting that demand is highly elastic at the current low ownership rate. Finally, we evaluate the net fiscal impact of the tax incentive and find that the tax deductibility of LTC insurance premiums leads to a net revenue loss for the government, as the reduced tax revenue from granting the tax incentive exceeds the savings in Medicaid's LTC expenditures.     

A convergent validity test within the payment card format using simulation techniques

A convergent validity test is performed between two groups of versions of the payment card format. The first group, the classic payment card (CPC), asks respondents to report their willingness to pay (WTP) as a point from a list of amounts, and then treats each WTP response as an interval. The second group generates WTP data that may contain both single point and interval values. It includes the two-way-payment ladder (TWPL) (respondents have to tick amounts they would definitely pay and cross amounts they would definitely not pay), and point-interval payment card (PIPC) (respondents have to tick their WTP as either a point or an interval). The test is conducted using data from one TWPL study and two PIPC studies. For each study, we use WTP values stated to simulate 200 CPC WTP datasets, which allows controlling for any behavioral biases likely to confound the outcome of the test. The results challenge the conventional way of eliciting WTP under the CPC and the typical way of treating WTP data from this PC version. Although convergent validity holds between the TWPL/PIPC and CPC, parameter and mean WTP estimates from the TWPL and PIPC are more stable as PC intervals widths increase.     

WILLINGNESS TO PAY FOR AIR QUALITY: THE CASE OF OUTDOOR EXERCISE

This study uses a contingent valuation (CV) survey to establish a sample of outdoor exercisers' willingness to pay (WTP) for ambient air quality improvements in East Baton Rouge parish, Louisiana. Estimated annual median and mean WTP values are £95 and £191, respectively, per person per year for assurance that ozone levels would not become "unhealthful" on any day. The survey informed respondents that in the prior year the local community experienced 14 days on which ozone levels exceeded federal standards. The study makes the strong assumptions that respondents believed they were "buying" 14 more healthy days and that WTP per day "bought" is constant. Given these assumptions, one can scale this WTP response to represent annual medians and means of approximately £7 and £14 per person per day, respectively. An econometric procedure for generalizing the community's annual WTP to avoid the 14 unhealthful days yields estimates ranging from £3.21 and £5.36 per person per healthy day, or between £12.4 and £20.6 million per year. The unit day estimates are comparable to CV and household production finction estimates of WTP in the Los Angeles basin, suggesting their usefulness for benefits transfer .     

Valuing climate protection through willingness to pay for biomass ethanol

This study uses a multi-part, split-sample contingent valuation method (CVM) and fair share (FS) survey to better understand the public's valuation of mitigating global climate change through its willingness to pay for biomass or “cellulosic” ethanol. In addition to a basic CVM question, a related scenario was developed that asked half of the survey respondents to state their fair share cost to lessen a potential food shortage in the next decade, also through the expanded use of cellulosic ethanol. Three alternative biomass feedstocks were assessed: farming residues, forestry residues and paper mill wastes, and municipal solid wastes. Overall a slightly larger proportion of respondents were WTP extra for cellulosic ethanol in the basic CVM scenario than in the FS scenario, though no significant differences were found in the WTP for the different feedstocks. Bid curve lognormal regression results for the two models were similar, supporting the idea that asking a FS rather than a conventional WTP question may be justifiable in some circumstances, such as in cases of a national emergency.     

An Experimental Validation of Hypothetical WTP for a Recyclable Product

Using a within-subject experiment, we compare hypothetical andreal willingness to pay (WTP) for an improvement in therecyclability of a product. Subjects are faced with a real paymentscenario after they have responded to a hypothetical question.Contrary to most of the results obtained in similar studies, at apopulation level, there are no significant median differencesbetween actual and hypothetical stated values of WTP. However,within-subject comparisons between hypothetical and actual valuesindicate that subjects stating a low (high) hypothetical WTP tendto underestimate (overestimate) the value of their actualcontributions.     

The effect of experience and quantity-based pricing on the valuation of a curbside recycling program

Quantity-based pricing for garbage collection services and recycling programs are becoming increasingly popular methods of meeting municipal solid waste diversion objectives. This article investigates household willingness to pay (WTP) for a pilot curbside recycling program (CRP) in the presence of a quantity-based pricing scheme for garbage collection services, which allows a household to alter their garbage container size at a reduced price. Unlike previous studies that have modeled the simultaneity of these household decisions as a two-step process, we jointly estimate the household's intentions using a full-information maximum-likelihood (FIML) approach. Our results show a strong positive correlation between a household's WTP for a CRP and its stated intention to reduce its garbage container size when a CRP is offered. The positive correlation suggests that WTP will be higher for households which are more likely to reduce their garbage container size. Thus, in the presence of quantity-based pricing, a household's WTP for recycling more fully reflects the marginal social costs of garbage disposal.     

Cognitive ability and scale bias in the contingent valuation method

This study investigates whether or not the scale bias found in contingent valuation (CVM) studies on mortality risk reductions is a result of cognitive constraints among respondents. Scale bias refers to insensitivity and non-near-proportionality of the respondents’ willingness to pay (WTP) to the size of the risk reduction. Two hundred Swedish students participated in an experiment in which their cognitive ability was tested before they took part in a CVM-study asking them about their WTP to reduce bus-mortality risk. The results imply that WTP answers from respondents with a higher cognitive ability are less flawed by scale bias.     

Dealing with preference uncertainty in contingent willingness to pay for a nature protection program: A new approach

In this paper, we propose an alternative preference uncertainty measurement approach where respondents have the option to indicate their willingness to pay (WTP) for a nature protection program either as exact values or intervals from a payment card, depending on whether they are uncertain about their valuation. On the basis of their responses, we then estimate their degree of uncertainty. New within this study is that the respondent's degree of uncertainty is “revealed”, while it is “stated” in those using existing measurement methods. Three statistical models are used to explore the sources of respondent uncertainty. We also present a simple way of calculating the uncertainty adjusted mean WTP, and compare this to the one obtained from an interval regression. Our findings in terms of determinants of preference uncertainty are broadly consistent with a priori expectations. In addition, the uncertainty adjusted mean WTP is quite similar to the one derived from an interval regression. We conclude that our method is promising in accounting for preference uncertainty in WTP answers at little cost to interviewees in terms of time and cognitive effort, on the one hand, and without researcher assumptions regarding the interpretation of degrees of uncertainty reported by respondents, on the other.     

The missing piece: Valuing averting behavior for children's ozone exposures

Individuals can reduce their exposure to air pollution by reducing the amount of time they spend outdoors. Reducing outdoor time is an example of an averting behavior that should be measured as part of willingness to pay (WTP) for improvements in air quality. In this paper, we estimate parents’ WTP to prevent restrictions on a child's outdoor time from a stated-preference (SP) conjoint survey. We combine this WTP measure with an estimate of reductions in time spent outdoors on high-ozone days from an activity-diary study to estimate this averting behavior component of WTP for reductions in ozone pollution.     

Public-good valuation and intra-family allocation

I derive values of marginal changes in a public good for two-person households, measured alternatively by household member i’s willingness to pay (WTP) for the good on behalf of the household, WTP _i (H), or by the sum of individual WTP values across family members, WTP(C). Households are assumed to allocate their resources in efficient Nash bargains over private and common household goods. WTP _i (H) is then defined by trade-offs between the public good and the household good, and WTP(C) by trade-offs of between the public good and private goods. WTP _i (H) is found to be higher (lower) than WTP(C) when member i has a relatively high (low) marginal valuation of the public good, but tends on average to equal WTP(C). As a consequence, individuals tend to represent households correctly on average when questioned about the household’s WTP for a public good, even when they are purely selfish and answer truthfully. Adding all members’ WTP answers on behalf of the household then leads to double counting. Pure and paternalistic altruism (the latter attached to consumption of the public good) move each member’s WTP on behalf of the household closer to the true sum of individual WTP, but only paternalistic altruism raises this sum.      

The Economic Value of Air-Pollution-Related Health Risks in China: A Contingent Valuation Study

The economic value of preventing adverse health effects related to air pollution is estimated using contingent valuation in three diverse locations in China. Values are estimated for three health endpoints: cold, chronic bronchitis, and fatality. Alternative statistical models are tested to study their impact on estimated willingness to pay (WTP) and on the relationship between WTP and respondent characteristics. Using the official exchange rate, the sample-average median WTP to prevent an episode of cold ranges between US$3 and US$6, the WTP to prevent a statistical case of chronic bronchitis ranges between US$500 and US$1,000, and the value per statistical life ranges between US$4,000 and US$17,000. Estimated mean values are between two and thirteen times larger. Our estimates are between about 10 and 1,000 times smaller than estimates for the US and Taiwan using official exchange rates. Indoor air quality, measured for a subset of respondents, shows no consistent relationship with WTP.     

Marginal WTP and Distance Decay: The Role of ‘Protest’ and ‘True Zero’ Responses in the Economic Valuation of Recreational Water Quality

We evaluate the sensitivity of distance decay in individuals’ stated willingness to pay (WTP) for water quality improvements in eutrophied lakes. We extend the standard model of contingent valuation (CV) by allowing individuals to adopt a sequential evaluation process consisting of two decision stages. In the first stage respondents decide whether they are ‘protesters’, have a WTP   \(=\)   ‘true zero’ or a \(\hbox {WTP}>0\) . Conditioned on a strictly positive WTP, we use Lee’s selectivity-corrected model to determine the magnitude of their WTP in the second stage. Using CV survey data from Norway we find significant distance decay in the first stage classification of respondents as ‘protesters’, ‘true zero’ WTP, or positive WTP. In the second stage model for positive WTP responses, we find little or no significant relationships when correcting for selection. Results suggest that previous findings of significant distance decay in contingent valuation of lake and river water in Europe may be driven by the definition of ‘protest’ and ‘true zero’ respondents. We find that WTP for water quality may be more useful as a qualitative indicator of political support for user financed water quality measures, than as a cardinal measure of marginal utility of water quality improvements.     

Reference Dependence Effects on WTA and WTP Value Functions and Their Disparity

In this study we investigate two reference dependence effects in a choice experiment. The first is the effect of the well-known distinction between gains and losses, the second is the effect of changing the reference value on willingness to pay (WTP) and willingness to accept (WTA). The latter has to our knowledge not been studied before. We hypothesize that there are differences between WTA and WTP, and that both value functions and their disparity are affected by the absolute value of the reference point. We test our hypotheses using a choice experiment with trade-offs between changes in flood probabilities and costs. The choice experiments elicit WTP and WTA, using two flood probability reference values, yielding four separate value functions. Our findings show that a substantial WTA–WTP disparity exists, and that this disparity increases when moving away from the reference point. Also, both WTA and WTP value functions are affected by the flood probability reference value, and the WTA–WTP disparity increases when the flood probability reference point increases. Both findings suggest that welfare effects caused by changes in public good provision depend not only on the direction of change (loss aversion), but also the reference value. Moreover, our results show that the latter effect is larger for losses than for gains. We introduce the concept of reference point updating as a possible explanation for these findings.     

Proportionality of Willingness to Pay to Small Changes in Risk: The Impact of Attitudinal Factors in Scope Tests

Sensitivity (proportionality) of willingness to pay (WTP) to (small) risk changes is often used as a criterion to test for valid measures of economic preferences. In a contingent valuation (CV) study conducted in Austria, 1,005 respondents were asked their WTP for preventing an increase in the risk of being killed in an avalanche of 1/42,500 and 3/42,500 respectively. WTP for the higher variation in risk is significantly greater than WTP for the lower risk change. We find evidence that those respondents who have had personal experience of avalanches in recent years combine the information about future risk increase—as provided in the survey—with the observed number of fatal avalanche accidents in the past. Proportionality of WTP holds if such prior experience is taken into account and if attitudinal factors in scope tests are controlled for. This research was funded by alpS GmbH—Center for Natural Hazard Management, Innsbruck, Austria.