Grantee Research Project Results
Final Report: Valuing Reduced Asthma Morbidity in Children
EPA Grant Number: R829665Title: Valuing Reduced Asthma Morbidity in Children
Investigators: Hanemann, Michael , Brandt, Sylvia
Institution: University of California - Berkeley , University of Massachusetts - Amherst
EPA Project Officer: Hahn, Intaek
Project Period: May 14, 2002 through December 31, 2006
Project Amount: $328,205
RFA: Valuation of Environmental Impacts on Children's Health (2001) RFA Text | Recipients Lists
Research Category: Human Health , Children's Health , Environmental Justice
Objective:
This economic study models household willingness-to-pay to minimize a specific health endpoint: morbidity in children with asthma (defined as asthma symptoms including coughing, wheezing and/or shortness of breath, limitations in activities, and psycho-social stresses). The project addresses three main questions: 1) what averting and/or mitigating actions do households take, 2) what are households’ stated willingness-to-pay for a reduction in their children’s asthma morbidity, and 3) what determines households’ perceptions of risks to an asthmatic child.
Study design
The primary contingent valuation studies of willingness to pay to reduce asthma morbidity are Rowe and Chestnut (1986) and O'Conor and Blomquist (1997). Unlike these previous asthma valuation studies this project is designed specifically for valuation of children’s morbidity. Additionally, we address two issues raised in the health valuation literature: 1) the validity of the assumption of fully informed and rational consumer behavior in the context of choices about health risks trade-offs (Cameron, 1999) and 2) estimation bias in models of households’ behavior due to omitted variables (see Atkinson and Crocker, 1992 and Harrington and Portney, 1987).
We combined an economic study on risk-reducing and -averting behavior with epidemiological and demographic data collected as part of the Fresno Asthmatic Children’s Environment Study (FACES). FACES is a five-year epidemiological study of approximately 250 households with asthmatic children aged 5-11, funded by the California Air Resources Board. The primary focus of FACES is to evaluate the impact of environmental factors such as air pollution on the natural history of childhood asthma. FACES follows households over multiple years and will incorporate the most detailed socio-demographic, indoor air quality and pollution monitoring data collection effort to date.
Discussion questions for focus groups were based on relevant domains from Social Cognitive Theory (SCT) and the Theory of Reasoned Action, and we used a grounded theory methodology to identify themes. After the focus groups reached theoretical saturation we designed and then administered a detailed survey on household attitudes, risk reducing behaviors, and market purchases. Using these data, we conducted a second series of focus groups to evaluate the content validity of alternative hypothetical scenarios. The contingent valuation (CV) survey was then administered to the same sample that completed the prior household behaviors survey.
The contingent valuation survey presented the household with a hypothetical monitor, worn like a watch, that provides constant feedback on the child's pulmonary function. The materials provided to the family explain that the watch would decrease the number of asthma days by 50%. The respondent was then reminded of the number of days with asthma symptoms they reported in a previous section of the survey and the number of asthma days the watch would be expected to have prevented. In our sample there was a mean of 16 days/month and 5 nights/month with asthma symptoms. The respondent was asked whether he or she would be willing to pay certain specific amounts for this monitor. We used a one-and-one half bounded format where participants were presented with a range of two possible prices and asked whether they would pay one or both prices for the monitor. We had a total of six pairs of prices [ (30,60) (20, 65) (15, 55) (5, 90) (80,100) (90, 125) ].
This scenario differs from previous CV scenarios used in health valuations in three dimensions. First, rather than presenting the respondent with a hypothetical policy change that would affect pollution or provision of health services and subsequently the child's health, our scenario presents a health product that would be directly used by the family. We took this approach to avoid two sources of unobserved heterogeneity --- household perceptions of the effectiveness of the policy and of the child's responsiveness to pollution. Second, to avoid confounding the willingness-to-pay (WTP) response with pre-existing preferences for health inputs, our scenario does not depend on any type of medication. Third, our hypothetical scenario targets both the dominant asthma impact (pain to child) by reducing the number of asthma attacks and the second most dominant quality of life impact (parental stress from uncertainty) by providing objective information.
Summary/Accomplishments (Outputs/Outcomes):
The household behaviors survey coupled with the epidemiological data revealed that: 1) households greatly overestimate the responsiveness of their child's asthma symptoms to air quality; 2) families engage in clusters of averting and mitigating actions which are not separable, and they have highly variable subjective assessments of the effectiveness of these behaviors; 3) families have varied preconceptions about the effectiveness and safety associated with prescription and nonprescription drugs, and prefer to minimize their use; 4) and uncertainty due to episodic symptoms significantly decreased household welfare. We used these revealed preference data to construct a hypothetical market good that filled the demand for a health product that is currently missing from the actual market.
We used the CV survey to elicit willingness to pay for reduced asthma morbidity. Respondents were very familiar with similar oxygen monitors commonly used (95% reported being familiar with a finger-clip style oxygen monitor), and prior to being presented a price for the hypothetical product 87% of respondents were interested in more information. We asked all respondents both closed-ended and open-ended questions on why they reported that they would or would not be willing to pay for the watch, how the product would benefit their family, and if they had any concerns. The overwhelming majority reported only asthma-related benefits (preventing an asthma episode or improved information). This is important because in previous studies using changes in air quality as the policy to be evaluated, it is not clear whether people value only health impacts of the policy or at the same time they value benefits of the policy not necessarily related to health. Only two respondents reported non-asthma benefits ("the watch would also tell time"). The primary reason families gave for not buying the watch at the offered price was that the child's asthma was not significant enough to warrant the purchase (n=30), followed by budget constraints (n=29).
We use both a nonparametric Turnbull estimator and a parametric logit model to estimate the survival function. The lower-bound mean WTP for a 50% reduction in symptoms using the Turnbull estimator is $66.73/month, or a conservative estimate of $696/year, for a mean reduction of 96 days and 30 nights a year. The mean WTP in the traditional parametric model is $68.50/month. By extending the spike model of Kriström (1997) to the one-and one-half bounded case we get a mean WTP of $63/month.
The two most comparable studies are Rowe & Chestnut (1986) and O’Conor & Blomquist (1997). Our estimates are significantly lower than the Rowe and Chestnut estimates of approximately $800/year for a mean 37-day reduction in bad days (all estimates from prior literature are converted to 2007 dollars using the CPI). This difference may not be surprising because the Rowe and Chestnut estimates are for eliminating the extreme end of the distribution of asthma symptoms. A second source of difference is that the Rowe and Chestnut study used a general scenario in which a government (local, state or federal) would reduce pollen, dust, air pollution and other asthma triggers by an undetermined mechanism. It is reasonable that while our scenario was designed to focus the households only on asthma symptoms, the Rowe and Chestnut scenario elicited preferences for environmental amenities and a range of symptoms that are often related and confounded with asthma, such as allergies.
Using two alternative hypothetical drugs to treat symptoms, O’Conor & Blomquist estimate a willingness to pay of approximately $1,300 to $4,900 a year for a 100% reduction in symptoms. If we were to simply double our estimates as a rough estimate of a WTP for a 100% reduction, our estimate is close to their lower bound, even though our sample differs markedly on socioeconomic variables. The O'Conor and Blomquist sample was predominately white, well-educated females with a higher mean income than the US mean and without children with asthma. Unlike their sample, households in our study all had with children with asthma, were racially mixed, had a wide range of education, varied in the language spoken at home, and had a mean household income lower than the US mean. It is reasonable to believe that our sample's mean WTP would lie near the lower range of the O'Conor and Blomquist range due to a lower mean ability to pay relative to households in their sample.
Applications
Valuing improvements in health is notoriously difficult, because of the need to present participants with a realistic choice whose effect is carefully calibrated to the health issue in question. The design of any valuation experiment can have a major impact on its accuracy and therefore its outcome. By using multiple series of focus groups and surveys, we designed a valuation scenario that carefully measures households' willingness to pay for a specific, quantifiable outcome: reduction in days with asthma systems. This approach can be extended throughout the field to calculate better estimates of the actual value of improved health outcomes, and therefore to establish or more sound basis for public policy decisions.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 5 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Brandt S, Lavin F, Hanermann M. Contingent Valuation Scenarios for Chronic Illnesses:The Case of Childhood Asthma. VALUE IN HEALTH 2012;15(8):1077-1083. |
R829665 (Final) |
Exit Exit |
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Mussio I, Brandt S, Hanermann M. Parental beliefs and willingness to pay for reduction in their child's asthma symptoms:A joint estimation approach. Health Economics 2020;30(1):129-143 |
R829665 (Final) |
Exit |
Supplemental Keywords:
Health, children’s health, economics, air pollution, behavioral science research, exposure, risk, risk assessment, effects, health effects, human health, sensitive populations, children, public policy, decision making, cost benefit, observation, nonmarket valuation, contingent valuation, survey, psychological, preferences, socioeconomic, willingness-to-pay, sociological, economics research, social sciences research,, RFA, Scientific Discipline, Economic, Social, & Behavioral Science Research Program, Health, Geographic Area, Health Risk Assessment, State, Susceptibility/Sensitive Population/Genetic Susceptibility, Environmental Monitoring, Allergens/Asthma, Ecological Risk Assessment, decision-making, Children's Health, genetic susceptability, Economics & Decision Making, Social Science, social psychology, surveys, behavioral effects, asthma, contingent valuation, sensitive populations, social impact analysis, valuation, morbidity, random utility model, air toxics, economic valuation, decision analysis, incentives, ozone, behavioral assessment, airway disease, risk perception, children's health values, preference formation, air pollution, environmental values, survey, airway inflammation, children, willingness to pay (WTP), adult valuation of children's health, asthmatic children, psychological attitudes, environmental health hazard, children's environmental health, environmentally caused disease, stated preference, willingness to pay, California (CA), economic objectives, behavior reactions, asthma morbidityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.