The Willingness to Accept Value of Statistical Life Relative to the Willingness to Pay Value: Evidence and Policy Implications

Large disparities between willingness to accept (WTA) and willingness to pay (WTP) based values of statistical life are commonly encountered in empirical studies. Standard economic theory suggests that if a public good is easily substitutable there should be no marked disparity between WTA and WTP values for the good, though the disparity increases with reduced substitutability. However, psychologists have shown that people often treat gains and losses asymmetrically and tend to require a substantially larger increase in wealth to compensate for a loss than the amount they would be willing to pay for an equivalent gain. Although most transport projects may aim to improve safety, situations arise when a relaxation of an existing regulation saves resources but increases the risk of death and injuries. A survey was recently carried out in New Zealand to determine people’s willingness to pay to reduce road risks and their willingness to accept compensation for an increase in risk. This paper reports the disparity observed between the two measures and considers some of the problems posed for policymakers.     

Values of Gains and Losses: Reference States and Choice of Measure

The available empirical evidence continues to suggest that people commonly value losses more, and often much more, than otherwise commensurate gains. Consequently, current practice of using the WTP measure for all changes is often likely to lead to misleading assessments of welfare changes. The reference dependence of preferences implies instead that while the WTP measure is appropriate for gains, the value of both positive and negative changes in the domain of losses will usually be more accurately assessed with the WTA measure.     

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.     

When expectations become aspirations: reference-dependent preferences and liquidity constraints

A large body of literature suggests that consumers derive utility from gains and losses relative to a reference point. This paper shows that such reference dependence can affect savings in opposite directions depending on whether people face liquidity constraints. Existing models for wealth and intertemporal choice predict that reference dependence reduces savings, but these models abstract from liquidity constraints. Introducing a liquidity constraint, I find that reference dependence can increase optimal savings for people without access to credit. Ex post, after reference points have been formed, liquidity constraints force consumers to take part of an income loss in early periods, inducing those who are reference dependent to concentrate the full loss in early periods and save in order to eliminate future losses. Further, anticipating a liquidity constraint raises the expected level of future consumption and thus the expectations-based reference point for future periods, creating an ex-ante savings motive. These findings underscore that it is important to account for financial market imperfections when applying or testing reference-dependent models in low-income settings, and potentially explain heterogeneity in how much the poor save when facing binding liquidity constraints.     

Testing competing models of loss aversion: an adversarial collaboration

This paper reports an ‘adversarial collaboration’—a project carried out by two individuals or research groups who, having proposed conflicting hypotheses, seek to resolve their dispute. It describes an experiment which investigates whether, when individuals consider giving up money in exchange for goods, they construe money outlays as losses or as foregone gains. This issue bears on the explanation of the widely observed disparity between willingness-to-pay (WTP) and willingness-to-accept (WTA) valuations of costs and benefits, which has proved problematic for contingent valuation studies. The results of the experiment are broadly consistent with the hypothesis that money outlays are perceived as losses.     

Endowment effect theory,prediction bias and publicly provided goods: an experimental study

Many studies report on a systematic disparity between the willingness to pay for a certain good (WTP) and the willingness to accept retribution payments in exchange for giving up this good (WTA). Thaler [Thaler RH (1980) J Econ Behav Organ 1:39–60] employs prospect theory to explain this disparity. The literature contains two different interpretations of his endowment effect theory. Accordingly, the disparity is caused either by the disutility from parting with one’s endowment and/or by an extra utility from ownership which is not anticipated by individuals who are not endowed with the good. So far, the empirical evidence on the applicability of endowment effect theory is limited to private goods. This paper reports on an experiment which finds a significant ownership utility effect for a publicly provided good. This result indicates that prospect theory applies to publicly provided goods even though consumers do not have exclusive property rights.      

The Aggregation of Climate Change Damages: a Welfare Theoretic Approach

The economic value of environmental goods is commonly determined using the concepts of willingness to pay (WTP) or willingness to accept (WTA). However, the WTP/WTA observed in different countries (or between individuals) will differ according to socio-economic characteristics, in particular income. This notion of differentiated values for otherwise identical goods (say, a given reduction in mortality risk) has been criticized as unethical, most recently in the context of the 'social cost' chapter of the IPCC Second Assessment Report. These critics argue that, being a function of income, WTP/WTA estimates reflect the unfairness in the current income distribution, and for equity reasons uniform per-unit values should therefore be applied across individuals and countries. This paper analyses the role of equity in the aggregation of climate change damage estimates, using basic tools of welfare economics. It shows one way of how WTP/WTA estimates can be corrected in aggregation if the underlying income distribution is considered unfair. It proposes that in the aggregation process individual estimates be weighted with an equity factor derived from the social welfare and utility functions. Equity weighting can significantly increase aggregate (global) damage figures, although some specifications of weighting functions also imply reduced estimates. The paper also shows that while the postulate of uniform per-unit values is compatible with a wide range of 'reasonable' utility and welfare specifications, there are also cases where the common-value notion is not compatible with defensible welfare concepts.     

Despairing Over Disparities: Explaining the Difference Between Willingness to Pay and Willingness to Accept

This paper examines the three major explanations for the disparity between willingness-to-pay (WTP) and willingness-to-accept (WTA) observed in contingent value surveys and laboratory experiments: a belief that the results must be biased in some fashion, Hanemann's (1991) substitutes hypothesis, and the loss aversion model proposed by Tversky and Kahneman (1991). Starting from the assumption that individuals make utility maximizing choices, we develop structural equations that yield parametric tests of the hypotheses within a single, non-experimental framework. The approach is flexible enough to incorporate a variety of functional form and distributional assumptions and can be applied to either data from either open-ended bids or dichotomous choice questions. The usefulness of the approach is demonstrated using data from a survey that asked both WTP and WTA questions. The results provide weak support for loss aversion.     

Modelling the Non-market Environmental Costs and Benefits of Biodiversity Projects Using Contingent Valuation Data

CV studies rarely ask willingness to accept (WTA)questions, yet there are a range of environmentalprojects where there are likely to be potential losersas well as gainers. This paper presents evidence fromsix biodiversity projects that the inclusion ofcontingent compensation payments from thoserespondents who preferred the status quo cansubstantially reduce net project benefits, even whenthe proportion of losers is relatively small. Astatistical model for estimating the mean welfaremeasure from dichotomous choice data which allows forboth positive WTP, zero WTP, and WTA is described. Asmany environmental projects are likely to create bothgainers and losers, we recommend that CV analysts giveserious consideration to the collection and analysisof WTA data otherwise they risk generating biasedestimates of project benefits.     

Auction mechanisms and the measurement of WTP and WTA

We evaluate the impact of three auction mechanisms — the Becker–DeGroot–Marschak mechanism, the second-price auction, and the random nth-price auction — in the measurement of willingness to pay (WTP) and willingness to accept (WTA) measures of value. Our results show that initial bidding in trial 1 in each auction does not contradict the endowment effect; but that, if it is the endowment effect that governs people’s initial bidding behavior, it can be eliminated with repetitions of a second-price or random nth-price auction; and if the thesis is that the effect should persist across auctions and across trials is right, our results suggest that there is no fundamental endowment effect.     

The Effect of Risk Characteristics on the Willingness to Pay for Mortality Risk Reductions from Electric Power Generation

The objective of this study is to estimate willingness to pay (WTP) for the reduction of mortality risks caused by fossil fuel (natural gas, coal and oil) versus nuclear electric power generation systems and to examine the influence of risk characteristics involved with electric power generation on WTP. A choice experiment was conducted to achieve these objectives. The attributes for nuclear risks in the experiment included the probability of disasters and the expected losses if a disaster occurs. We find evidence of (i) a baseline effect (where WTP is sensitive to hypothetical versus actual baseline expected mortality); (ii) a ‘labeling effect,’ where, surprisingly, the term ‘nuclear’ has no effect on WTP, but the term ‘fossil-fueled power generation’ results in lower WTP; and (iii) disaster aversion, meaning that people focus on the conditional loss from a nuclear disaster, not the probability. We also find that the WTP for reducing deaths from a nuclear disaster is about 60 times the WTP for routine reducing fossil-fuel generation-related deaths.     

Money matters: an axiomatic theory of the endowment effect

We develop a framework that allows us to state precisely the relationship between leading concepts of the theoretical and empirical research on reference-dependent preferences, namely the status quo bias, the endowment effect and the willingness to accept (WTA)/willingness to pay (WTP) gap. We show that a monetary version of the status quo bias is a necessary condition for the WTA/WTP gap, and show how to factor out the part of the gap due to income effects from the part of the gap due to the endowment effect. As a byproduct, we show that reference-dependent phenomena are generated by reference-independent factors, i.e., an underlying reference-independent preference relation the properties of which are discussed at length.     

Optimistic irrationality and overbidding in private value auctions

Bidding one’s value in a second-price, private-value auction is a weakly dominant solution (Vickrey in J Finance 16(1):8–37, 1961), but repeated experimental studies find more overbidding than underbidding. We propose a model of optimistically irrational bidders who understand that there are possible gains and losses associated with higher bids but who may overestimate the additional probability of winning and/or underestimate the potential losses when bidding above value. These bidders may fail to discover the dominant strategy—despite the fact that the dominant strategy only requires rationality from bidders—but respond in a common sense way to out-of-equilibrium outcomes. By varying the monetary consequences of losing money in experimental auctions we observe more overbidding when the cost to losing money is low, and less overbidding when the cost is high. Our findings lend themselves to models in which less than fully rational bidders respond systematically to out-of-equilibrium incentives, and we find that our model better fits the effects of our manipulations than most of the existing models we consider.     

WTA Estimates Using the Method of Paired Comparison: Tests of Robutness

The method of paired comparison is modified to allow choices between two alternative gains so as to estimate willingness to accept (WTA) without loss aversion. The robustness of WTA values for two public goods is tested with respect to sensitivity of the WTA measure to the context of the bundle of goods used in the paired comparison exercise and to the scope (scale) of the public good project. There was no statistical difference in WTA measures for open space based on independent treatments with different contexts. One treatment involved valuing open space within a set of goods with similar value. The other treatment involved valuing open space within a choice set of goods which had lower dollar values than open space. There was a statistical difference in WTA between a permanent expansion in the bus system and a temporary expansion in the bus system. We conclude the method of paired comparison appears to be a very promising approach to elicit measures of WTA.     

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.     

Response Strategies and Learning in Discrete Choice Experiments

This study explores ordering effects and response strategies in repeated binary discrete choice experiments. Mechanism design theory and empirical evidence suggest that repeated choice tasks per respondent induce strategic behaviour. We find evidence that strategic opportunities provided by the order in which choice sets are presented to respondents affect choice decisions (strategic response). The results suggest, however, that respondents may solely respond to high cost rather than low cost inconsistencies. That is, respondents are more cost sensitive, and thus have a lower willingness to pay (WTP), if the same or a similar level of provision was offered in a previous choice set at a lower cost than if it was not. Yet, the cost sensitivity, and thus WTP, remains unaffected if the same or a similar level of provision was offered in a previous choice set at a higher cost. Our findings further indicate that cost sensitivity increases (and thus WTP decreases), when respondents progress through the choice task, with this increase (decrease) lessening as more choice questions are answered. Possible explanations are value learning and strategic learning.     

Measuring Stigma: The Behavioral Implications of Disgust

Stigmatization of products and technologies can lead to large monetary losses even when there are no associative risks. This paper reports on experiments that provide insight into the behavioral responses of disgust from an economic perspective. We use a dead sterilized cockroach to ‘contaminate’ drinking water and generate willingness-to-pay (WTP) and willingness-to-accept (WTA) measures of participants’ reactions. These results are contrary to previous results from research not involving financial incentives, as most participants’ WTP and WTA values are near zero for drinking cockroach contaminated water. Additionally, filtration of cockroach water leads participants to become significantly more likely to request compensation compared to spring water, but it does not result in requesting significantly more money to drink it. Finally, WTP and WTA differences can be explained by participants’ decision on whether or not to request compensation and not by the amount of compensation.     

Comparing Fuzzy and Probabilistic Approaches to Preference Uncertainty in Non-Market Valuation

In seeking to value environmental amenities and public goods, individuals often have trouble trading off the (vague) good or amenity against a monetary measure. Valuation in these circumstances can best be described as fuzzy in terms of the amenity being valued, perceptions of property rights, and the numbers chosen to reflect values. In this paper, we apply fuzzy logic to contingent valuation, employing a fuzzy clustering approach for incorporating preference uncertainty obtained from a follow-up certainty confidence question. We develop a fuzzy random utility maximization (FRUM) framework where the perceived utility of each individual is fuzzy in the sense that an individual’s utility belongs to each cluster to some degree. The model is then applied to a Swedish survey that elicited residents’ willingness to pay for enhanced forest conservation and to a Canadian survey of agricultural landowners that elicited their willingness to accept compensation for a tree planting program. Both the WTP and WTA measures we obtain using the fuzzy approach are well below those obtained using standard probability methods. Based on goodness of fit measures and Monte Carlo experimentation, a case can be made for using a fuzzy preference approach for modeling preference uncertainty as opposed to incorporating respondent uncertainty within the random utility maximization framework.      

Using the travel cost method to value visits and stigma in connection with ARV adherence in Uganda

This article uses the travel cost method to value both client visits to collect antiretroviral therapy (ARV) and stigma, which prevents ARV adherence. Using a representative sample for Uganda initiated specifically for this study, we found a willingness to pay (WTP) valuation for visits made in the range of US$14–US$17 and a willingness to accept (WTA) valuation of US$25 for visits missed. The valuations for stigma based on a novel measure of stigma using a new estimation method were close to the valuations for visits. These valuations can be used to estimate the benefits to carry out cost–benefit analyses (CBAs) of interventions aimed at increasing ARV coverage and adherence.     

Sensitivity of Willingness to Pay Estimates to the Level of Attributes in Discrete Choice Experiments

This paper considers issues raised in the application of discrete choice experiments (DCEs) to estimating willingness to pay (WTP). The main issue addressed is the sensitivity of WTP estimates to the level of attributes. A DCE, concerned with preferences for alternative cervical screening programmes, was carried out with women in the Tayside area of Scotland. A split sample design was employed in which respondents were divided into two groups. Each group received a discrete choice questionnaire that varied with respect to the levels of three of the six attributes. The price attribute was one of the attributes that varied across questionnaires. Whilst estimated coefficients were not significantly different across five of the six attributes included in the experiment, mean WTP estimates were significantly different for four of the five welfare estimates. However, from a policy point of view, such a difference may not be important. Consideration is also given to other general methodological and policy issues that are raised when using DCEs to estimate WTP. The findings suggest the need for further research into the design and application of DCEs as a method for estimating WTP.