UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR

SCIENCE ADVISORY BOARD

July 29, 2011

EPA-SAB-11-011

Honorable Lisa P. Jackson

Administrator

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Washington, D.C. 20460

Subject: Review of Valuing Mortality Risk Reductions for Environmental Policy: A White Paper

(December 10, 2010)

Dear Administrator Jackson: 

The EPA’s National Center for Environmental Economics (NCEE) requested the Science Advisory 

Board’s (SAB) advice on how the Agency should value mortality risk reductions in its benefit-cost

analyses of environmental policy. The NCEE asked the SAB to review its White Paper entitled 

“Valuing Mortality Risk Reductions for Environmental Policy” (December 2010). To respond to this 

advisory request, the SAB’s Environmental Economics Advisory Committee (EEAC) was augmented 

with additional experts with expertise in valuing mortality risk reductions. 

The White Paper recognizes a longstanding problem with the term “value of statistical life” (VSL). A 

“statistical life” has traditionally referred to the aggregation of small risk reductions across many 

individuals until that aggregate reflects a total of one statistical life. For example, a one year decrease in 

average risk of mortality in the U.S. of 1 in a million would result in 310 “statistical lives” saved (given 

a population of 310 million). The VSL has been a shorthand way of referring to the monetary value or 

tradeoff between income and mortality risk reduction, i.e. the willingness to pay for small risk 

reductions across large numbers of people, but it has led to confusion because many have interpreted it 

as referring to the loss of identified lives. In recognition of the confusion and controversy caused by the 

VSL term, the White Paper proposed replacing the VSL term with “value of mortality risk.” The SAB

enthusiastically endorses a terminology change, but in our view, a term like “value of risk reduction” 

(VRR) would better communicate the notion that value is derived from reducing risks rather than the 

risks themselves. While the SAB recommends this terminology, we recognize that we are not experts in 

risk communication and suggest that EPA consider focus groups or some other mechanism to explore 

the language that best communicates this concept to the public. Public engagement is needed to dispel 

common misconceptions around this issue. 
When valuing risk reduction, it is important to communicate exactly what kind of risk is being reduced 

since the public may value reducing risk of one kind of mortality (e.g., cancer mortality) differently 

from reducing risk of another kind (e.g., traumatic injury). The White Paper notes that research suggests 

that people are willing to pay more for mortality risk reductions that involve cancer than for risk 

reductions from accidental injury, and proposes a placeholder value that could be used for this cancer 

differential while the Agency pursues long-term research to differentially value other types of risks. The 

SAB agrees that values for risk reductions are not “one size fits all” and endorses the Agency’s proposal 

to apply different values to different type of risk contexts. The SAB encourages the Agency to explore 

alternative methods identified in this report for estimating these context-specific values from the 

available research base. 

The White Paper correctly notes that the amount of money people would be willing to pay for “public” 

risk reductions (that affect everyone) can differ from willingness to pay for “private” risk reductions 

(that affect only the individual or household). While this is conceptually true, the empirical literature is 

not yet sufficiently developed to be able to adapt values for altruistic concerns in benefit-cost analysis. 

Thus, at present, the SAB recommends that EPA include estimates of willingness to pay for both public 

and private risk reductions without distinguishing between the two. 

The SAB was asked a number of technical questions about EPA’s database of mortality risk reduction 

values and the most appropriate statistical approach for deriving a value for mortality risk reduction 

from existing studies. In this report, the SAB offers specific recommendations on criteria that should be 

used to select studies for inclusion in the database. The report also discusses how these studies could be 

used in meta-analysis or other approaches to estimate appropriate values of risk reduction. The SAB 

supports the Agency’s plan to update its estimates for valuing risk reduction on a regular basis. The 

estimates that the Agency currently uses are based on studies that are at least 20 years old and do not 

take into consideration the wealth of newer studies that make use of better techniques, better data, and 

that better reflect current conditions. To avoid using estimates based on outdated research in the future, 

the Agency should establish a protocol for updating regularly the estimates of the value of risk reduction 

that it uses in its work.

Lastly, this SAB report does not address the complex social and political context for benefit-cost 

analysis in environmental policy. The White Paper described the valuation challenge facing the Agency 

and the different contexts underlying existing mortality risk reduction values. Thus, the SAB EEAC

applied its expertise toward the analytic and empirical challenges described in EPA’s eight charge 

questions and thus limited its scope to these topics. It should be noted that the Agency’s White Paper

only addressed valuing mortality risk reductions for adults. Accordingly, the SAB did not address the 

challenges associated with valuing children’s risk reductions except to encourage the Agency to devote 

resources to research on this deserving topic. 
Thank you for the opportunity to provide advice on this White Paper. The SAB looks forward to 

receiving the Agency’s response. 

Sincerely, 

/signed/ /signed/

Dr. Deborah L. Swackhamer Dr. Catherine L. Kling

Chair Chair 

Science Advisory Board Environmental Economics Advisory Committee

Enclosures
i

NOTICE

This report has been written as part of the activities of the EPA Science Advisory Board, a public 

advisory committee providing extramural scientific information and advice to the Administrator 

and other officials of the Environmental Protection Agency. The Board is structured to provide 

balanced, expert assessment of scientific matters related to problems facing the Agency. This 

report has not been reviewed for approval by the Agency and, hence, the contents of this report 

do not necessarily represent the views and policies of the Environmental Protection Agency, nor 

of other agencies in the Executive Branch of the Federal government, nor does mention of trade 

names or commercial products constitute a recommendation for use. Reports of the EPA Science 

Advisory Board are posted on the EPA Web site at: http://www.epa.gov/sab. 
ii

U.S. Environmental Protection Agency

Environmental Economics Advisory Committee

Augmented for the Review of Valuing Mortality Risk Reduction

CHAIR

Dr. Catherine Kling, Professor, Department of Economics, Iowa State University, Ames, IA

MEMBERS

Dr. Trudy Ann Cameron, Raymond F. Mikesell Professor of Environmental and Resource 

Economics, Department of Economics, University of Oregon, Eugene, OR

Dr. Maureen L. Cropper, Professor, Department of Economics, University of Maryland, College 

Park, MD

Dr. Nicholas Flores, Professor, Department of Economics, Arts and Sciences, University of 

Colorado, Boulder, Boulder, CO

Dr. James K. Hammitt, Professor, Center for Risk Analysis, Harvard University, Boston, MA

Dr. F. Reed Johnson, Distinguished Fellow and Principal Economist, RTI Health Solutions, 

Research Triangle Institute, Research Triangle Park, NC

Dr. Madhu Khanna, Professor, Department of Agricultural and Consumer Economics, University 

of Illinois at Urbana-Champaign, Urbana, IL

Dr. Karen Palmer, Senior Fellow, Resources for the Future, Washington, DC

Dr. George Parsons, Professor, School of Marine Science and Policy and Department of 

Economics, University of Delaware, Newark, DE

Dr. Laura Taylor, Professor, Department of Agricultural and Resource Economics, North 

Carolina State University, Raleigh, NC

Dr. Peter J. Wilcoxen, Associate Professor, Economics and Public Administration, Syracuse 

University, Syracuse, NY

Dr. JunJie Wu, Emery N. Castle Professor of Resource and Rural Economics, Department of 

Agricultural and Resource Economics, Oregon State University, Corvallis, OR

Dr. Jinhua Zhao, Professor, Department of Agricultural, Food and Resource Economics, 

Michigan State University, East Lansing, MI
iii

SCIENCE ADVISORY BOARD STAFF

Dr. Holly Stallworth, Designated Federal Officer, EPA Science Advisory Board Staff Office, 

Washington, D.C.
iv

U.S. Environmental Protection Agency

Science Advisory Board

BOARD

CHAIR

Dr. Deborah L. Swackhamer, Professor and Charles M. Denny, Jr. Chair in Science, 

Technology and Public Policy, Hubert H. Humphrey School of Public Affairs and Co-Director of 

the Water Resources Center, University of Minnesota, St. Paul, MN

SAB MEMBERS

Dr. David T. Allen, Professor, Department of Chemical Engineering, University of Texas, 

Austin, TX

Dr. Claudia Benitez-Nelson, Full Professor and Director of the Marine Science Program, 

Department of Earth and Ocean Sciences , University of South Carolina, Columbia, SC

Dr. Timothy J. Buckley, Associate Professor and Chair, Division of Environmental Health 

Sciences, College of Public Health, The Ohio State University, Columbus, OH

Dr. Patricia Buffler, Professor of Epidemiology and Dean Emerita, Department of 

Epidemiology, School of Public Health, University of California, Berkeley, CA

Dr. Ingrid Burke, Director, Haub School and Ruckelshaus Institute of Environment and Natural 

Resources, University of Wyoming , Laramie, WY

Dr. Thomas Burke, Professor, Department of Health Policy and Management, Johns Hopkins 

Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD

Dr. Terry Daniel, Professor of Psychology and Natural Resources, Department of Psychology, 

School of Natural Resources, University of Arizona, Tucson, AZ

Dr. George Daston, Victor Mills Society Research Fellow, Product Safety and Regulatory 

Affairs, Procter & Gamble, Cincinnati, OH

Dr. Costel Denson, Managing Member, Costech Technologies, LLC, Newark, DE

Dr. Otto C. Doering III, Professor, Department of Agricultural Economics, Purdue University, 

W. Lafayette, IN

Dr. David A. Dzombak, Walter J. Blenko, Sr. Professor of Environmental Engineering , 

Department of Civil and Environmental Engineering, College of Engineering, Carnegie Mellon 

University, Pittsburgh, PA
v

Dr. T. Taylor Eighmy, Vice President for Research, Office of the Vice President for Research, 

Texas Tech University, Lubbock, TX

Dr. Elaine Faustman, Professor and Director, Institute for Risk Analysis and Risk 

Communication, School of Public Health, University of Washington, Seattle, WA

Dr. John P. Giesy, Professor and Canada Research Chair, Veterinary Biomedical Sciences and 

Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Dr. Jeffrey K. Griffiths, Professor, Department of Public Health and Community Medicine, 

School of Medicine, Tufts University, Boston, MA

Dr. James K. Hammitt, Professor, Center for Risk Analysis, Harvard University, Boston, MA

Dr. Bernd Kahn, Professor Emeritus and Associate Director, Environmental Radiation Center, 

Georgia Institute of Technology, Atlanta, GA

Dr. Agnes Kane, Professor and Chair, Department of Pathology and Laboratory Medicine, 

Brown University, Providence, RI

Dr. Madhu Khanna, Professor, Department of Agricultural and Consumer Economics, 

University of Illinois at Urbana-Champaign, Urbana, IL

Dr. Nancy K. Kim, Senior Executive, Health Research, Inc., Troy, NY

Dr. Catherine Kling, Professor, Department of Economics, Iowa State University, Ames, IA

Dr. Kai Lee, Program Officer, Conservation and Science Program, David & Lucile Packard 

Foundation, Los Altos, CA

Dr. Cecil Lue-Hing, President, Cecil Lue-Hing & Assoc. Inc., Burr Ridge, IL

Dr. Floyd Malveaux, Executive Director, Merck Childhood Asthma Network, Inc., Washington, 

DC

Dr. Lee D. McMullen, Water Resources Practice Leader, Snyder & Associates, Inc., Ankeny, 

IA

Dr. Judith L. Meyer, Professor Emeritus, Odum School of Ecology, University of Georgia, 

Lopez Island, WA

Dr. James R. Mihelcic, Professor, Civil and Environmental Engineering, University of South 

Florida, Tampa, FL
vi

Dr. Jana Milford, Professor, Department of Mechanical Engineering, University of Colorado, 

Boulder, CO

Dr. Christine Moe, Eugene J. Gangarosa Professor, Hubert Department of Global Health, 

Rollins School of Public Health, Emory University, Atlanta, GA

Dr. Horace Moo-Young, Dean and Professor, College of Engineering, Computer Science, and 

Technology, California State University, Los Angeles, CA

Dr. Eileen Murphy, Grants Facilitator, Ernest Mario School of Pharmacy, Rutgers University, 

Piscataway, NJ

Dr. Duncan Patten, Research Professor, Hydroecology Research Program , Department of Land 

Resources and Environmental Sciences, Montana State University, Bozeman, MT

Dr. Stephen Polasky, Fesler-Lampert Professor of Ecological/Environmental Economics, 

Department of Applied Economics, University of Minnesota, St. Paul, MN

Dr. Arden Pope, Professor, Department of Economics, Brigham Young University , Provo, UT

Dr. Stephen M. Roberts, Professor, Department of Physiological Sciences, Director, Center for 

Environmental and Human Toxicology, University of Florida, Gainesville, FL

Dr. Amanda Rodewald, Professor of Wildlife Ecology, School of Environment and Natural 

Resources, The Ohio State University, Columbus, OH

Dr. Jonathan M. Samet, Professor and Flora L. Thornton Chair, Department of Preventive 

Medicine, University of Southern California, Los Angeles, CA

Dr. James Sanders, Director and Professor, Skidaway Institute of Oceanography, Savannah, 

GA

Dr. Jerald Schnoor, Allen S. Henry Chair Professor, Department of Civil and Environmental 

Engineering, Co-Director, Center for Global and Regional Environmental Research, University 

of Iowa, Iowa City, IA

Dr. Kathleen Segerson, Philip E. Austin Professor of Economics , Department of Economics, 

University of Connecticut, Storrs, CT

Dr. Herman Taylor, Director, Principal Investigator, Jackson Heart Study, University of 

Mississippi Medical Center, Jackson, MS

Dr. Barton H. (Buzz) Thompson, Jr., Robert E. Paradise Professor of Natural Resources Law 

at the Stanford Law School and Perry L. McCarty Director, Woods Institute for the 

Environment, Stanford University, Stanford, CA
vii

Dr. Paige Tolbert, Professor and Chair, Department of Environmental Health, Rollins School of 

Public Health, Emory University, Atlanta, GA

Dr. John Vena, Professor and Department Head, Department of Epidemiology and 

Biostatistics, College of Public Health, University of Georgia, Athens, GA

Dr. Thomas S. Wallsten, Professor and Chair, Department of Psychology, University of 

Maryland, College Park, MD

Dr. Robert Watts, Professor of Mechanical Engineering Emeritus, Tulane University, 

Annapolis, MD

Dr. R. Thomas Zoeller, Professor, Department of Biology, University of Massachusetts, 

Amherst, MA

SCIENCE ADVISORY BOARD STAFF

Dr. Angela Nugent, Designated Federal Officer, U.S. Environmental Protection Agency, 

Science Advisory Board Staff Office, Washington, DC

Dr. Holly Stallworth, Designated Federal officer, U.S. Environmental Protection Agency, 

Science Advisory Board Staff Office, Washington, DC
viii

Table of Contents

1. EXECUTIVE SUMMARY .................................................................................................. 1

2. BACKGROUND ................................................................................................................... 4

3. GENERAL COMMENTS.................................................................................................... 5

4. RESPONSES TO CHARGE QUESTIONS........................................................................ 9

4.1. QUESTION 1 - TERMINOLOGY ........................................................................................... 9

4.2. QUESTION 2 – CANCER DIFFERENTIAL ............................................................................ 10

4.3. QUESTION 3 – PUBLIC AND PRIVATE RISK REDUCTION .................................................... 12

4.4. QUESTION 4 – STATED PREFERENCE AND HEDONIC WAGE STUDIES ................................. 13

4.5. QUESTION 5 – INCOME ELASTICITIES .............................................................................. 20

4.6. QUESTION 6 – STATISTICAL APPROACH........................................................................... 21

4.8. QUESTION 8 – BENEFIT FUNCTION TRANSFER APPROACH ................................................ 25

5. REFERENCES.................................................................................................................... 28

APPENDIX A: EPA’S CHARGE TO THE SAB.................................................................. A-1
1

1. EXECUTIVE SUMMARY

This report was prepared by the Science Advisory Board (SAB) Environmental Economics Advisory 

Committee Augmented for Valuing Mortality Risk Reduction (the “Committee”) in response to a 

request by EPA’s National Center for Environmental Economics (NCEE) to review its draft White Paper

“Valuing Mortality Risk Reductions for Environmental Policy” (December 10, 2010). The Committee, 

augmented with additional experts, deliberated on the charge questions during a January 20 – 21, 2011 a 

face-to-face public meeting and a subsequent public conference call on March 14, 2011 was approved 

by the Chartered SAB at a public teleconference call on June 7, 2011. Three topics were highlighted in 

the charge questions: EPA’s proposed terminology change, willingness to pay for cancer risk reductions, 

and the treatment of altruism. Other charge questions covered the selection criteria for inclusion in 

EPA’s database of studies, the income elasticity of mortality risk reduction values, EPA’s statistical 

approach for deriving an estimate, more timely updates to the Agency’s guidance, and other methods for 

valuing health risk reduction. This Executive Summary highlights the SAB’s major findings and 

recommendations.

EPA’s Proposed Terminology Change (Charge Question 1). The White Paper discusses problems 

associated with the popular misunderstanding of the “value of statistical life” (VSL) metric that has 

traditionally been used in benefit-cost analysis. The VSL concept arose in benefit-cost analysis to 

express society’s willingness to pay (WTP) for health risk reductions. Since environmental policies that 

reduce mortality risks also impose costs, information about the resulting benefits is necessary to 

determine whether the benefits of the improvements outweigh the costs. One category of benefits is 

captured by society’s willingness to pay for health risk reductions. Much indignation has been 

expressed in public and political settings over the VSL term because it is often perceived as the value of 

life itself or the value of an individual’s life when, in fact, the term is meant to refer to society’s 

willingness to pay for small changes in risk. In the jargon of economics, VSL describes individuals’

marginal rate of substitution between health risks and income or wealth. To better communicate this 

concept, SAB agrees with EPA that the Agency should move away from the traditional VSL term in 

favor of a new term that conveys the tradeoff between income and small reductions in health risk. 

While the SAB favors (and use in our advisory) a term like “value of risk reduction” (VRR) or “value of 

mortality risk reduction”, we encourage the Agency to undertake some research, possibly including

focus groups, on how best to communicate this tradeoff to the public. EPA needs a term that captures the 

value of small risk reductions that can be aggregated over large numbers of people, not a term that is 

easily confused with the value of life itself. In addition to finding ways to communicate the tradeoff

between income and health risk reductions, the SAB encourages the Agency to explain the type of risk 

to be reduced while seeking ways to differentiate willingness to pay for one kind of health risk reduction 

versus another. Since these values express demands for different goods by different groups of people, a 

single “one size fits all” metric used to express the marginal rate of substitution between health risks and 

income oversimplifies the many complex policy contexts in which EPA operates. 

Willingness to Pay for Cancer Risk Reductions (Charge Question 2). Reducing environmental cancer 

risk is an important part of EPA’s mission to protect human health. Thus a key question is how to 

account for individuals’ preferences for reducing cancer risks relative to other types of health risks. In 

addition to cancer, many other health threats addressed by environmental policies also consist of illness 

profiles with long latencies and substantial periods of morbidity prior to death. EPA has correctly noted 

that some research finds a “cancer premium,” i.e. a higher willingness to pay for cancer risk reductions 

than for other kinds of mortality risk reductions, though other good studies find no evidence of a 

differential. EPA asked the SAB to comment on a placeholder value that could be used for this cancer 
2

premium while the Agency pursues long-term research to differentially value different types of risks. 

The SAB believes that the “first-cut” estimate of a 50 percent differential for cancer should be refined 

before application. This refinement should take into account the different comparators used in current 

studies (e.g., fatal accident, chronic disease) and recognize that several good studies find small 

differences between cancer and other risks while others find large differences.

Building from the recognition that WTP to reduce cancer risks may differ from WTP to reduce other 

fatal health risks, the SAB recommends that EPA work toward developing a set of estimates of VRR 

corresponding to policy-relevant contexts defined by the type or characteristics of the risk (e.g., 

associated morbidity, latency) and of the affected population (e.g., age, health, income). Economic 

theory and empirical evidence suggest that WTP can vary with these characteristics and that a single 

value of mortality risk reduction is not appropriate for all contexts. Developing this set of estimates will 

be challenging because the available empirical estimates do not cover all relevant contexts and there is 

substantial, poorly understood variation among estimates from different studies. The SAB describes

several methods for developing this set of estimates and encourages EPA to evaluate the validity and 

relevance of these methods for informing policy analysis. Proposed approaches include: (1) using only 

primary estimates obtained for the specific context; (2) developing adjustment factors to transfer 

estimates from other contexts; (3) developing meta-regression equations and (4) structural benefittransfer methods to characterize appropriate values across multiple contexts.

Altruism (Charge Question 3) EPA asked us to comment on how altruism should be treated in valuing 

risk reductions for environmental policy. The White Paper correctly notes that the amount of money 

people would be willing to pay for “public” risk reductions (that affect everyone) can differ from 

willingness to pay for “private” risk reductions (that affect only the individual). Differences may be a 

result of altruism, either paternalistic or pure (also called non-paternalistic). Pure altruism occurs when 

altruists respect the preferences of the beneficiary and care about the net welfare effect on the 

beneficiary. Paternalistic altruism occurs when benefactors substitute their own preferences for that of 

the beneficiary, e.g., care about the risk reduction but not about any costs imposed on the beneficiary. 

The literature is clear that values driven by paternalistic altruism should be counted while values driven 

by pure altruism need not be counted as they do not affect the sign of net benefits. (Preferences 

concerning the distribution of benefits or costs in the population affect the evaluation and should be 

counted.)

Although the theory is clear, economic analysis has not evolved to the point of being able to separately 

measure portions of total value attributable to paternalistic and non-paternalistic altruism. In addition,

there is little empirical evidence that altruistic concerns are significant drivers of values for risk 

reduction. Thus, at present, the SAB recommends that EPA include estimates of willingness to pay for 

both public and private risk reductions without distinguishing between the two.

Database Development (Charge Question 4). EPA asked the SAB about inclusion criteria for its 

database of stated preference and hedonic wage studies. Specific recommendations are offered in 

response to EPA’s questions about selection criteria and weaknesses in data sets in the attached report. 

With regard to concerns about whether and how to combine results from stated preference and revealed 

preference studies, the SAB judges that the distinction between study type is less important than 

accounting for differences in risk and individual characteristics. 

Income Elasticities (Charge Question 5). The Agency asks for advice concerning procedures for 

updating its values to account for income growth. The SAB notes that the decision on how to adjust 

values of risk reduction (VRR) for income growth over time is related to the approach used to estimate
3

the VRR (or range of VRRs) for a particular application. The SAB recommends developing estimates 

of income-elasticity as part of the process used to estimate appropriate VRRs for different contexts 

described above.

Updating Values of Risk Reduction (Charge Questions 6 and 7). The Agency requested guidance on 

whether it was sensible to use a simplified approach for updating the values of risk reduction using a set 

of available studies to fit a parametric distribution. The SAB strongly endorses EPA’s proposal to 

update VRR estimates routinely as improved information becomes available and urges the Agency to 

establish a protocol for regular updates. The current estimates depend upon studies that are 20 – 35 

years old and it is time to take advantage of a wealth of new studies and better data. In principle, any of 

the methods described above for estimating VRRs in different contexts could be updated to include new 

literature. 

Long-Term Research (Charge Question 8). To support improved value estimates in the longer term, the 

SAB encourages EPA to work toward using structural preference functions, although the SAB believes 

that it will be some time before such an approach will be ready for implementation. The Agency also 

should encourage research to obtain revealed and stated preference estimates for the types of risk and 

types of affected populations that are most relevant to environmental policy contexts.
4

2. BACKGROUND

Reductions in mortality risk constitute the largest quantifiable benefits category of many of EPA’s rules 

and regulations. As such, mortality risk valuation estimates are an important input to EPA’s benefit cost 

analyses. EPA has historically used a value of statistical life (VSL) to express the benefits of mortality 

risk reductions in monetary terms for use in benefit cost analyses of its rules and regulations. EPA has 

used the same central default value (adjusted for inflation) in its primary analyses since 1999 when the 

Agency updated its Guidelines for Preparing Economic Analyses (2000). EPA’s Guidelines advise 

analysts to use a central VSL estimate of $4.8 million in 1990 dollars which converts to $6.2 million in 

2002 dollars. 

Prior to the release of the Guidelines, EPA sought advice from the Science Advisory Board (SAB) on 

the appropriateness of this estimate and its derivation. In 2000, EPA also consulted with SAB on the 

appropriateness of making adjustments to VSL estimates to capture risk and population characteristics 

associated with fatal cancer risks (USEPA 2000). The SAB

responded with the report, ‘‘An SAB Report on EPA’s White Paper Valuing the Benefits of Fatal 

Cancer Risk Reduction’’ (EPA–SAB–EEAC–00–010). In 2004, EPA consulted with the SAB on 

questions related to appropriate methodologies for valuing life extensions of different lengths and the 

use of meta-analysis to combine estimates from the literature. In 2006, the SAB reviewed an EPA paper 

on the application of meta-analysis techniques to deriving estimates for the value of mortality risk

reduction as well as a paper on appropriate and available methods for

valuing mortality risk reductions when affected populations have relatively short remaining life 

expectancy. In 2007, the SAB responded with ‘‘SAB Advisory on EPA’s Issues in Valuing Mortality 

Risk Reduction’’(EPA–SAB–08–001). 

In 2010, EPA’s National Center for Environmental Economics issued its draft White Paper “Valuing 

Mortality Risk Reductions for Environmental Policy: A White Paper (December 2010) and requested an 

SAB review. Augmented with additional experts, the SAB’s Environmental Economics Advisory 

Committee met on January 20 – 21, 2011 to deliberate on NCEE’s questions (found in Appendix A) and 

teleconferenced on March 14, 2011 to finalize its draft report. This report was approved by the 

chartered SAB on June 7, 2011. 
5

3. GENERAL COMMENTS

To frame the responses to the charge questions, this report provides some perspective on the concept of 

valuing mortality risk reduction and its use in estimating the benefits of environmental policies. This 

perspective is followed by responses to the specific charge questions.

The economic theory concerning valuation of reductions in mortality risk is well developed but 

application to evaluation of environmental policies is challenging. First, there is a limited set of 

empirical studies available for reliably determining values of mortality-risk reduction and how these 

values depend on characteristics of the risk and affected population. Second, the conventional term used 

to describe the value of risk reduction (the “value of a statistical life,” or VSL) is easily misinterpreted, 

leading to confusion about key concepts. As discussed below, the SAB applauds EPA’s proposal to 

adopt an alternative to the conventional term and use the term “value of risk reduction” (VRR) in our 

discussion.

From an economic perspective, VRR is an individual- and risk-specific value defined as the individual’s 

marginal rate of substitution between money and mortality risk. It has units of dollars per change in 

probability of death in a specified time period (e.g., the current year). This marginal rate of substitution 

can be used to estimate the money value of a small change in risk (by multiplying the change in 

probability by the rate); analogously, the rate is often estimated from information about the monetary 

value that an individual judges to be equivalent to a small change in risk.

VRR is often characterized using the maximum amount an individual could pay for a risk reduction 

without making himself worse off. In other words, an individual’s willingness to pay (WTP) for a risk 

reduction ∆p is defined as the amount of money such that the individual is indifferent between his initial 

position (with initial risk and wealth) and a position in which his mortality risk (in the specified period)

is reduced by ∆p and his wealth is reduced by WTP. Alternatively, one can define VRR using the 

amount of money the individual would require as compensation to forgo a risk reduction; i.e., he is 

indifferent between having his initial wealth with the risk reduction ∆p, and forgoing the risk reduction 

but having his wealth increased by his willingness to accept compensation (WTA). For the small risk 

changes that are usually relevant to environmental policy, these two estimates of VRR (WTP/∆p and 

WTA/∆p) should be nearly equal.1

First, the amount of money an individual judges as equivalent to a change in risk (both WTP and WTA)

should be larger for a larger risk change. Moreover, for small changes in risk (for which WTP or WTA

is a small share of wealth or income), the money value should be nearly proportional to the risk change, 

which is equivalent to saying the rate of substitution between money and the change in risk is nearly 

Economic theory implies that VRR is likely to depend on characteristics of the individual and the risk. 

Five key implications of standard theory for valuing mortality risk are highlighted below. 

 1 In this example, WTP is the compensating variation and WTA is the equivalent variation for the risk reduction. One can 

also define VRR using WTA compensation for a risk increase (i.e., compensating variation for a risk increase) and WTP to 

prevent a risk increase (i.e., equivalent variation for a risk increase). Under conventional economic theory, these two values 

of VRR should be identical to the two defined in the text for infinitesimally small risk changes. Empirically, estimates of 

WTA are often much larger than estimates of WTP, as discussed in response to charge question 4.a.i (Stated Preferences 

Studies). 
6

constant (e.g., if a risk reduction of one in one million is worth $10, then an otherwise similar risk 

reduction of two in one million is worth $20).2

Recognizing that VRR is a metric that can vary with both individual and risk characteristics, the 

conceptually appropriate method to estimate the benefits to the U.S. population of a change in mortality 

risk that results from environmental policy is to estimate the risk changes faced by each individual over 

time, value these changes using the appropriate individual VRRs, and sum the results over the 

population. In contrast, an alternative “short-cut” approach is conventionally applied. The short-cut 

approach is to multiply the number of people in the population by the population-mean risk reduction 

(yielding the number of “lives saved”) and multiply that by the population-mean VRR. The short-cut 

Second, VRR depends on the individual’s wealth or income, i.e., on his ability to pay. It seems intuitive 

and is consistent with economic theory and empirical evidence that a richer person will generally be 

willing to pay more for (and demand greater compensation to forgo) a risk reduction.

Third, VRR is likely to depend on other individual characteristics, such as age, life expectancy, future 

health prospects, responsibility to care for dependents, and other factors. Intuitively, the benefit of 

surviving the current period depends on the future conditions one is likely to face, and the opportunity 

cost of spending money to improve survival (or of accepting compensation to forgo an improvement) 

depends on other demands on an individual’s wealth. For these factors, however, economic theory does 

not provide clear implications and empirical estimates are limited in coverage and quality.

Fourth, VRR is likely to depend on other characteristics of the risk, including both objective and 

subjective characteristics. Objective characteristics include latency (time between exposure and 

subsequent illness or death) and the duration and severity of associated morbidity (these attributes can 

be described as an “illness profile”). Subjective characteristics include the extent to which the hazard 

which presents the risk is perceived as under the individual’s control, voluntarily accepted, familiar, 

well-understood, and dreaded. Again, theory and empirical evidence provide only limited information 

on how these factors affect VRR. 

Fifth, the monetary value to an individual of any given program to reduce mortality risk may also 

depend on program characteristics in addition to the individual’s personal risk reduction. For example, 

individuals may have different values for risk reductions provided through public goods that affect other

people (such as cleaner ambient air) and risk reductions provided through private goods that affect only 

themselves or their households (cleaner indoor air at their residence). Their values may also depend on 

the distribution of risk reductions within the population (e.g., whether disadvantaged populations are 

disproportionately affected) and the mechanism through which costs are paid (e.g., income taxes, 

electricity prices). 

 2 Many stated-preference studies estimate that the rate of substitution between money and risk change varies substantially 

with the magnitude of otherwise similar small risk changes. If this finding accurately represents individuals’ preferences, it 

implies that individuals’ indifference curves between wealth and the probability of surviving the specified time period are 

sharply curved or kinked within the range of survival probabilities in question. It seems implausible that different individuals, 

facing different initial mortality risks, will have sharp curves or kinks in their indifference curves in precisely the small

regions needed to account for this empirical finding and more plausible that the finding reflects a limitation of statedpreference methods. Sharply diminishing marginal WTP with the size of the risk reduction implies that an individual would 

value a second risk reduction of ∆p much less than an initial risk reduction of ∆p. This seems unreasonable, from the 

perspectives of economic theory and common sense, except when payment for the initial risk reduction substantially reduces 

ability to pay for the second increment. If it were accepted as a valid description of individual preferences, then valuation of 

environmental policies would need to account for it by using sharply different VRRs for individuals obtaining larger and 

smaller risk reductions (Hammitt and Treich 2007).
7

approach yields an approximation to the conceptually appropriate method. It requires information on

only the average VRR and risk reduction, not on how VRR and risk reduction vary across individuals.

The approximation is exact when any of three conditions hold: (a) all individuals face the same risk 

reduction; (b) all individuals have the same VRR; or (c) individual risk reductions and VRRs are 

uncorrelated in the population. If none of these conditions holds, the short-cut approach introduces bias

as a result of “premature aggregation” (Cameron 2010, Hammitt and Treich 2007).

Because appropriate valuation of reductions in mortality risk generally requires information on how 

VRR varies among individuals and with risk characteristics, the SAB recommends that EPA orient its 

approach toward (a) recognizing the conceptually appropriate method to estimate population benefits 

and (b) developing a set of estimates of VRR for policy-relevant cases characterized by risk and 

individual characteristics (or a function relating VRR to risk and individual characteristics). This 

orientation would be a departure from the older notion of identifying “the value of a statistical life” that 

is appropriate for policy evaluation. (EPA has already moved away from this older notion, e.g., by 

recognizing that cancer risks may be valued differently than fatal injury risks.) The SAB recognizes that 

developing a set of context-specific VRRs will be challenging, due to limitations of the empirical 

literature. This implies that, for the near term, place-holder values will be needed for many contexts, 

perhaps obtained using VRRs estimated for other contexts with or without adjustment. Nevertheless, the 

SAB recommends that economic evaluation of environmental policies specify the conceptually 

appropriate approach and explicitly acknowledge the necessity to apply pragmatic proxies for that ideal 

given data limitations.

Conceptually appropriate, context-specific estimates of VRR should account for uncertainty about the 

VRR for each case, ideally as a probability distribution. Developing this set of estimates is challenging 

because of limited theoretical guidance and empirical evidence concerning how VRR varies with risk 

and individual characteristics. Moreover, estimates of VRR are highly variable, both within and between 

studies. This variability makes it difficult to distinguish differences in VRR associated with risk and 

individual characteristics from random variation and from differences in study design. Many effects of 

study characteristics on VRR estimates are not well understood. In estimating the VRR for each case, 

one confronts a tradeoff between using only studies that are specifically relevant to that case and using 

estimates for other cases, whether neighboring or more distant, perhaps by estimating a functional 

relationship of values to risk and individual characteristics. The former choice will tend to minimize bias 

at the cost of higher variance, especially variance of the difference in valuation between cases. It may 

even lead to illogical differences in VRR between cases. The latter choice will tend to increase bias but 

reduce variance and provide a smoother relationship between values and characteristics.

While it is clear from economic theory that individual WTP may vary with individual and risk 

characteristics, the SAB acknowledges that the objectives, methods, and principles underlying benefitcost analysis and particularly the values of mortality risk reductions and other non-market goods are 

often misunderstood or rejected as inappropriate by many participants and commentators on the policymaking process. In the past, for example, the Agency was criticized for considering VRRs that differ by 

individuals’ age. However, as acknowledged in the White Paper, values for health risk reductions are 

not “one size fits all.” Applying a willingness to pay value to a targeted population (such as low income 

or elderly) that exceeds that group’s willingness to pay for reduced risk could result in decisions that 

ultimately reduce the well-being of the targeted group. The proposed change of terminology and 

application of VRRs that differ with individual and risk characteristics provide an opportunity for 

constructive engagement with the public and other interested parties concerning these topics.
8

Finally, the SAB notes that the White Paper and most of the charge questions concern technical issues 

concerning methods for valuing reductions in mortality risk to adults for use in benefit-cost analysis. 

The SAB did not engage in a broader evaluation of the appropriateness of benefit-cost analysis for 

evaluating environmental regulations, methods for valuing mortality risk reductions to children, or other 

topics that were outside the scope of the White Paper and charge questions. While the White Paper

focuses on values for risk reductions for adults, values of reducing children’s risk are not as well 

understood, thus this is a topic deserving of EPA’s attention and resources for research.
9

4. RESPONSES TO CHARGE QUESTIONS

4.1. Question 1 - Terminology

Current EPA guidelines and standard practice use “Value of Statistical Life” (VSL) as the metric 

for valuing mortality risks. Section 3.1 of the White Paper discusses the VSL terminology 

commonly used in mortality risk valuation exercises in greater detail. The White Paper suggests 

that the Agency move away from using the traditional VSL terminology in favor of a new term for 

estimates of the marginal rate of substitution between health risks and income (see section 3.1). 

Specifically, the White Paper suggests that the Agency refer to these estimates as the “value of 

mortality risk,” and report the associated units using standard metric prefixes to indicate the size of 

the risk change, e.g., $/mr/person/yr (dollars per milli[10-3]-risk per person per year), or 

$/μr/person/yr (dollars per micro[10-6]-risk per person per year), etc. Does the Committee agree 

that the Agency should pursue such a change? Does the Committee believe that making these 

changes would ease or exacerbate the misunderstandings documented by Cameron (2010)? Would 

some other terminology or approach be preferable? Please explain.

The SAB strongly supports replacing the “value of statistical life” (VSL) with a term that more 

accurately reflects what is being measured. The SAB encourages EPA to consider replacing VSL 

with “value of risk reduction” (VRR) and using VRR to delineate different types of risk. For 

example, there might be a VRR for sudden workplace death, a VRR for cancer death, a VRR for 

heart disease, and so forth. VRRs might also vary demographically (e.g., a VRR for cancer death 

for men 40 to 50 years old). The SAB chose not to recommend standard units but did discuss 

micro-risk, milli-risk and nano-risk as obvious possibilities. The best units to use will depend on 

the policy context, the level of aggregation, and the way in which VRR will be used.

The EPA’s White Paper proposed the terminology “value of mortality risk” (VMR) to replace VSL. The 

SAB believes that the new term should include “reduction” since the value is typically derived from a 

reduction in risks rather than from the risks themselves and used to value risk reductions. Also, VMR

gives the impression that people have a positive value for risk. Using risk reduction avoids this 

confusion. The SAB also believes that using “mortality” does not always provide a complete description 

of the risks involved. Different types of risks are often intertwined in valuation studies and policies 

often lead to changes in mortality as well as morbidity risks. For example, the morbidity (and other 

factors such as dread) associated with cancer is difficult to separate from the mortality risk of cancer. 

Excluding “mortality” allows for VRRs that encompass a broader array of health risks. As noted above, 

the SAB suggests that VRRs for morbidity or mortality risks be accompanied by a policy-specific 

classification of the type of probabilistic outcome, the target population, etc. 

While the SAB recommends the terminology VRR, we recognize that we are not experts in 

communication. For this reason, the SAB suggest that EPA consider testing the VRR terminology and 

explore alternative terminologies in focus groups, discussions, and presentations with relevant user 

groups. Along these lines and in response to the public misconceptions of VSL documented in Cameron 

(2010), the SAB recommends EPA consider conducting or sponsoring research into effective 

communication of VRR and its role in benefit-cost analysis to the general public. Numerous public 

comments in response to an article about the VSL in the popular press suggest that many people also 
10

have difficulty with the use of the word “value.”3

4.2. Question 2 – Cancer Differential

Many non-economists seem to believe that the word 

value means “intrinsic worth,” rather than the economists’ notion of willingness to pay, and they bridle 

at the idea that their government would presume to put a dollar value on their lives. In any event, the 

change from VSL to something like VRR as well as the other suggested changes (e.g., from a single

value of VRR to values for specific policy-related risk changes) provide a prime opportunity to engage 

in effective public communication. There have been calls in the past for EPA to start research programs 

on public communication and recent developments in climate change communication further highlight 

the importance of public communication in the effectiveness of policy making and implementation. 

Regardless of the exact language chosen, the SAB believes that making such a change will contribute to 

easing the public misunderstanding of VSL. The SAB applauds EPA’s leadership in this suggestion.

Experts generally agree that value function transfers can outperform point value transfers in cases 

where the characteristics of the risks and/or the exposed populations differ between the source 

studies and the policy context in measurable ways. That is, the more commodity- and individualspecific attributes that can be included in the benefit transfer exercise, the better the estimate of 

willingness to pay. Charge questions 2 and 3 inquire about whether applications of benefits 

transfer methods to value mortality risk reductions from environmental pollutants can be improved 

by controlling for more of the attributes that distinguish the source studies from the policy scenario.

The White Paper concludes that research since the 2000 EPA Guidelines suggests that people are 

willing to pay more for mortality risk reductions that involve cancer than for risk reductions from 

accidental injury (see section 3.3). Our preliminary review suggests that a “cancer differential” of 

up to 50% over immediate accidental or “generic” risk valuation estimates may be reasonable. 

Conceptually, would the weight of evidence (both theoretical and empirical) suggest there is a 

cancer differential? If so, does the Committee believe that our estimate of the differential is 

appropriate If not, how does the Committee recommend the Agency incorporate cancer 

differentials in benefits analysis involving reduced cancer risks?

The SAB commends EPA for its effort to develop appropriate values for mortality risk reductions rather 

than applying a “one size fits all” value to all cases. As discussed in the introductory section, theory 

suggests that VRR depends on characteristics of the risk and the individual.

As noted, charge questions 2 and 3 inquire about the use of benefit-transfer methods. Charge questions 

4 – 7 are also concerned with issues of inferring the appropriate VRR for a specific application from 

available studies. As explained in the introductory section, SAB recommends that EPA work toward 

developing a set of estimates of VRR for policy-relevant cases characterized by risk and individual 

characteristics. There are strong precedents for applying benefit-transfer methods to analyze non-health 

benefits of EPA policies. In that context, as with VRR, analysts confront choices between how much to 

rely on estimates that are specific to the application and how much to “borrow information” or 

extrapolate from estimates that are less similar to the application (in the present context, how much to 

adjust for differences in attributes between the risk valued in source studies and the policy-relevant risk). 

There is no general answer to this problem. The best approach will be sensitive to the quality and 

number of available studies that estimate relevant values. In the case of death from traumatic injury, the 

 3 See Binyamin Appelbaum, “As U.S. Agencies Put More Value on a Life, Businesses Fret,” New York Times, February 16, 

2011 and the inventory of public comments available at 

http://pages.uoregon.edu/cameron/vita/Stakeholder_misconceptions.pdf.
11

set of empirical estimates is rich, including revealed-preference studies of wage differentials and

consumer products (e.g., motor vehicles) and stated-preference studies of transportation hazards. For 

other applications, the empirical literature is much more limited and often includes only statedpreference studies.

Given this background, SAB recommends that EPA explore alternative methods to estimate a 

distribution of appropriate VRRs for relevant cases (e.g., deaths associated with exposure to airborne 

fine particulate matter, fatal cancers associated with exposure to environmental carcinogens). Below, the 

SAB suggests four possible methods. It may be appropriate to use different methods for different policyrelevant cases to reflect differences in the number and quality of relevant studies and differences in the 

characteristics of the risk reductions they value.

One approach would be to develop independent estimates for relevant cases, using only studies that are 

closely matched on risk and individual characteristics. This approach may be useful for some cases but 

not others, due to the limited coverage of the empirical literature. 

A second approach would be to develop a baseline distribution of estimates (perhaps for fatal injury) and 

a set of adjustment factors for risk and individual characteristics as warranted. Such adjustment factors 

might be developed for hazard characteristics (e.g., one or more cancer differentials appropriate for 

different types of cancer), individual characteristics (e.g., adjustment factors for age and income), and 

program characteristics (e.g., public programs versus private risk reductions). This approach could 

incorporate both direct estimates of VRR for different risks and risk-tradeoff studies that estimate only 

differentials in VRR between risks. This approach and the first approach could be informed using formal 

expert elicitation to identify the studies that are sufficiently closely matched to the policy context of 

interest and/or to estimate distributions of baseline estimates and adjustment factors.

A third approach would be to develop a meta-regression model to estimate VRR as a function of risk 

and individual characteristics. The historical EPA approach, using the mean of 26 studies, is an example 

of a meta-regression including only one term (an intercept). This approach could be extended to include 

a small number of categorical or indicator variables (e.g., for cancer type, age or income categories) 

and/or a small number of continuous variables (e.g., income or its logarithm). It may be appropriate to 

include variables describing study type (notably stated or revealed preference) to avoid confounding 

estimates of risk and individual characteristics with (poorly understood) effects of study type (at 

minimum, one should test for sensitivity to study type). Such a meta-regression can be viewed as a 

reduced-form or first-order approximation of a more complicated function relating VRR to risk and 

individual characteristics. 

A fourth approach would be to develop and estimate a structural preference function. An advantage of 

this approach is that its structure is consistent with economic theory, and so extrapolation from existing 

estimates can be performed with greater confidence (e.g., it may be possible to develop improved 

estimates of how VRR depends on the magnitude of the risk reduction). Moreover, it provides a method 

for incorporating other types of information, in addition to estimates of VRR, that are informative about 

individual preferences regarding mortality risk reduction. (As described in response to charge question 

8, SAB judges that the structural-preference-function approach requires further development and testing 

before it should be relied on as a primary source of VRR estimates.)

In evaluating the different approaches, one criterion is the degree of fit between the resulting estimated 

distribution for VRR in each specific context and the results from high-quality studies that estimate 
12

VRR for that context directly. A second criterion is the intuitive plausibility of the pattern of VRR 

distributions across contexts.

In estimating VRRs and how they vary with risk and individual characteristics, the SAB suggests 

caution in using results from non-US populations. The effects of individual and population 

characteristics on VRRs may be sensitive to health-care and social-welfare programs and other factors

that differ significantly between countries.

In response to charge question 2, SAB recognizes that cancer is (after fatal injury) the risk for which the 

empirical literature provides the most information. In addition, there are some estimates of VRR for 

respiratory and other chronic disease. The SAB concurs with EPA’s judgment that only the studies that 

compare values for cancer and other risk reductions are useful for evaluating possible differentials. 

These include valuation studies of two or more types of fatal risk and risk-tradeoff studies. Stated- and 

revealed-preference studies of only one type of risk, without internal comparison, are not useful because 

there is too much unexplained variation between studies to determine how much of the differential is 

associated solely with risk characteristics. 

The SAB believes that the “first-cut” estimate of a 50 percent differential for cancer should be refined 

before application. This estimate is justified in the White Paper as approximating the average differential 

found in nine studies (reported in footnote 14, page 25). However, no control is made for the fact that 

different studies evaluate different types of cancer and compare it against different risks (e.g., injury, 

other disease) and the differential associated with the Van Houtven et al. (2008) study is misreported 

(the proportional WTP is 3 times higher but the differential is 2). Any quantitative estimate of a cancer 

differential will be sensitive to the weight given to the Van Houtven et al. study, which estimates a much 

larger effect than any of the other studies. (Note that six of the nine reported studies yield estimates 

between -0.15 and +0.30).

Finally, in evaluating hazard-specific differentials it is important to distinguish between differentials that 

are conditional on characteristics of the illness profile (e.g., duration and severity of morbidity, latency) 

and differentials that do not control for these characteristics. In evaluating values of faster vs. slower

deaths (e.g., from injuries vs. cancers), it seems important to control for whether the period of morbidity 

extends life or shortens the period of healthy life (i.e., is the comparison between instantaneous death 

and manifestation of a fatal disease at the same time or between instantaneous death and death from 

chronic disease at the same time?). In addition, some studies provide information on valuation of 

different types of cancer, suggesting that there is no single differential that is appropriate for all cancers.

In sum, the SAB suggests that the magnitudes of cancer and other hazard-specific differentials should be 

evaluated as part of an integrated process used to estimate the value of mortality risk reduction and how 

it varies with risk and individual characteristics, using some of the methods described above. 

4.3. Question 3 – Public and Private Risk Reduction

Environmental policies generally provide public risk reductions. However, research, particularly 

stated preference research, provides willingness to pay estimates for both public risk reductions as 

well as private risk reductions. And, some research indicates that individuals’ willingness to pay 

for public risk reductions may be different than that for private risk reductions. One factor that 

may contribute to these differences is altruism, which, all else equal, should make values for public 

risk reductions larger than those for private risk reductions. 
13

a. Should EPA rely on studies that estimate willingness to pay for both public and private risk 

reductions? If so, is it sufficient to control for this key characteristic in the modeling 

framework? Or, should EPA limit the analysis to studies according to the type of risk 

reduction in the study? If using only one type of study is recommended, should EPA use 

studies that estimate public or private risk reductions? If we are to limit the studies used to

one type, is there a role for the excluded group?

As described above, VRR may vary with program characteristics such as public or private risk 

reduction. The SAB does not recommend categorically restricting inference to studies that are only 

private or only public but exploring the estimated magnitude of the effect. If the effect is of sufficient 

magnitude to warrant accounting for it in economic evaluation of a program, it can be accounted for by 

using only studies that are closely matched to the required application or by adjusting results from other 

studies.

b. Studies that estimate willingness to pay for public risk reductions may allow EPA to better 

capture altruistic preferences in benefit-cost analysis. Did the White Paper adequately 

capture the theory on how to incorporate altruism into the value of mortality risk reduction? 

How should altruistic preferences be treated in benefit-cost analysis? Should the Agency 

incorporate altruism into the value of mortality risk reductions, even if we are unable to 

distinguish the specific form of altruism involved (i.e., paternalistic or non-paternalistic)? 

More generally, what alternatives should the Agency pursue in the short-term to 

appropriately account for altruistic preferences when evaluating public programs, if any? 

The White Paper adequately summarizes the literature on altruism in benefit-cost analysis. Values 

driven by paternalistic altruism are considered legitimate in benefit-cost analysis. The literature is clear 

that pure (non-paternalistic) altruism, in which the benefactor respects the preferences of the beneficiary, 

can result in over-counting benefits (e.g. Flores 2002, Bergstrom 2006). This is because welfare gains 

that accrue to beneficiaries, and that are valued by altruists, depend on the net value to beneficiaries. If 

beneficiaries were to pay exactly their value for a larger quantity of a public good, then altruists would 

receive no altruistic welfare gain. However if beneficiaries paid less (more) than their value, altruists

would receive an altruistic welfare gain (loss). In short, pure altruists care about both the benefits 

received and costs paid by beneficiaries; counting only the altruistic benefits is incorrect.

While the economic literature is clear on how values driven by paternalistic and non-paternalistic 

concerns should be treated in economic analysis, the state of the art in economic analysis has not 

evolved to the point of being able to separately measure portions of total value attributable to 

paternalistic and non-paternalistic altruism. There is little empirical evidence that altruistic concerns are 

significant drivers of values for risk reduction. At present, the SAB recommends that EPA include 

estimates of willingness to pay for both public and private risk reductions without distinguishing 

between the two.

4.4. Question 4 – Stated Preference and Hedonic Wage Studies

The two primary literatures used to assess willingness to pay for mortality risk reductions are 

stated preference studies and hedonic wage studies. The White Paper assembles two databases 

summarizing studies in both literatures, capturing much of the information outlined in number 3 of 
14

the SAB-EEAC’s recommendations dated October 2007 (see section 4).4

a. The selection criteria employed in creating the two data sets are carefully outlined in the 

paper (see sections 4.1.2 and 4.2.4). Please consider these criteria in answering the 

following questions:

 These studies, or a subset 

thereof, would form the basis of revised guidance in the near term as well as possible future metaanalyses. 

i. Should additional criteria be added to screen studies for inclusion in the datasets? If 

so, please specify those criteria. Should any criteria be eliminated or modified? 

The EPA assembled two databases summarizing stated preference and hedonic wage studies following 

the SAB-EEAC’s recommendations dated October 2007 (see especially Section 4). As noted in the 

charge question, these criteria are intended to be used to identify appropriate studies for estimating 

VRR, whether as part of a meta-analysis or using some other approach, such as those identified in 

response to charge question 2. A set of eight criteria was used to select studies to include in each 

database. The objective of the selection criteria -- to exclude low-quality studies and to ensure 

applicability to the US -- should be stated explicitly to ensure transparency and the selection of 

appropriate criteria. An additional criterion that should be added is that estimates should be restricted to 

those obtained for appropriate risk and population characteristics when that restriction is appropriate for 

the approach used to estimate VRR in a particular context (see the discussion of methods described in 

response to charge question 2). Below are answers for each of the specific charge questions for each 

database separately (where appropriate). Note also that the criteria apply to studies valuing of both 

morbidity and mortality since both types of endpoints are relevant to measuring VRRs in different 

contexts.

Stated Preferences Studies

With respect to stated preference studies, the SAB provides its response to the White Paper’s eight 

selection criteria. 

(1) Minimum sample size of 100.

The SAB believes that setting a minimum acceptable sample size is not a very useful 

criterion. Small samples are of concern for two reasons: the precision of the estimates is 

likely to be low and the sample is unlikely to adequately represent a population of interest. 

With regard to the first point, the relationship between sample size and precision of the 

estimated VRR depends on the study design, e.g., for a fixed sample size, one singlebounded binary-choice valuation question provides less precision than a double-bounded 

binary-choice question, which provides less precision than an open-ended question. (Note 

that the approaches that provide more precision may induce more bias and are not necessarily 

better.) Similarly, choice experiments in which respondents make many choices may provide 

more precision than contingent-valuation studies in which respondents value only a single 

good. These considerations suggest that different minimum sample sizes should be developed 

for different types of stated preference (SP) studies, thereby compromising the simplicity of a 

sample-size criterion. A conceptually cleaner approach would be to develop a criterion based 

on precision of the estimate. The SAB understands that some SP studies do not report the 

precision or standard error of their estimates or information from which this can be 

 4 The recommendations included specific features of hedonic wage and stated preference studies that should be identified in 

the studies. 
15

approximated. Studies that do not report quantitative information about the uncertainty in 

their estimates do not follow established best research practices and thus are not of adequate 

methodological quality for use in determining VRR. Moreover, such studies seem unlikely to 

meet other criteria for methodological adequacy, such as providing evidence that the results 

can be interpreted as valid estimates of VRR (discussed below). 

With regard to the second point, studies with small samples often use convenience samples 

or other groups that are not representative of the general population. These studies are likely 

to be excluded by the second criterion, discussed below. If a study with small sample size 

uses a sample that is representative of the population of concern and provides adequate 

precision, it should be included in the analysis.

(2) Sample frame based on general population.

The SAB suggests that the sample frame be the “appropriate population” rather than the 

general population, to the extent practicable. The EPA should be clear in its determination of 

what the appropriate sample frame is and seek studies that use that sample frame or can be 

used to understand how to adjust results that use other sample frames. For example, if the 

EPA is seeking to value reductions of risks that are specific to a particular segment of the

population, the study should focus on obtaining values that are relevant for members of that 

segment of the population. Older studies will eventually fail to adequately represent the 

current population so the age of the study should be evaluated to determine whether it is 

reasonable to consider it representative of current preferences.

(3) Conducted in a high-income country.

The SAB believes that surveys should ideally be limited to those conducted in the United 

States. To the extent that preferences, cultural norms, institutions, and demographic profiles 

can affect valuation of risk reductions, studies based on non-U.S. populations may provide 

biased estimates of U.S. values. Indeed, work using similar stated-preference instruments 

suggests there are significant differences in patterns of WTP even between countries as 

similar as the U.S. and Canada (Alberini et al. 2004, Cameron et al. 2010).

(4) Results based on exclusive dataset.

The SAB disagrees with this criterion. In economic research, multiple estimates for an 

outcome of interest (in this case, a point estimate of the VSL) are often reported which are 

based partially or wholly on overlapping samples. Model uncertainty, covariatemeasurement uncertainty, and interest in heterogeneity of impacts across subpopulations all 

lead to varying outcome estimates. Rather than apply a zero weight to the information 

contained in all but one of the estimates arising from a single database, or from overlapping 

databases, the SAB recommends that the EPA include estimates based on its set of other 

criteria and take all estimates that meet those criteria. If possible, EPA should control 

statistically for within-study correlations. 

(5) Written in English.

The SAB agrees with this criterion.

(6) Provides enough information to calculate a WTP estimate if one is not reported in the paper.

The SAB agrees with this criterion.
16

(7) Provides estimates for willingness to pay (willingness to accept estimates were not included).

The SAB agrees that contingent valuation studies of WTA often yield results that differ 

substantially from estimates of WTP (Horowitz and McConnell 2002). The presence of 

income effects can justify some of the difference between these value constructs, as could 

limited substitutability of market goods (Hanemann 1991), but the reasons for occasionally 

very large divergences are not clear. Thus the SAB recommends that contingent valuation 

estimates of WTA should not be used. A second rationale for this advice is that most 

environmental policies and regulations do not involve compensating individuals for 

environmental damages but rather individual willingness to pay the costs of policies or 

regulations that reduce mortality risk.

(8) Provides estimates for willingness to pay for risk reductions to adults (estimates for risk 

reductions to children are not included).

The SAB agrees that estimates of VRR for adults should be based on estimates of WTP for 

risk reductions to adults. Of course, the Agency also needs values for mortality-risk changes 

for children. VRR estimates for adults should not be automatically applied for children, so 

this criterion is not applicable in the case of children’s risks. The SAB recognizes that there 

is a paucity of studies focused on estimating the value of risk reduction for children. This is 

clearly a research need that the Agency may wish to invest in.

The SAB recommends an additional criterion: that the stated preference study should provide evidence 

that it yields valid estimates of VRR. There are many factors that can influence responses to a statedpreference survey in ways that cannot be interpreted as consistent with estimating the theoretical concept 

of interest. For example, respondents may give answers consistent with extraordinarily high or low 

values (e.g., “protest zeros” in open-ended questions). One form of evidence of validity is showing that 

the study passes a scope test, i.e., that estimated WTP increases with the size of the risk reduction that is 

valued. A weak scope test demands only that WTP increase in a statistically significant way with the 

size of the risk reduction; a strong test demands that WTP be proportional to risk reduction (for changes 

in mortality risk, economic theory implies that WTP is nearly proportional to the risk change with 

deviations occurring primarily through the income effect (Hammitt and Graham 1999, Corso et al. 

2001). External scope tests (that compare WTP between subsamples of respondents) are generally 

viewed as superior to internal scope tests (that compare WTP within a sample) because respondents 

could provide mutually consistent estimates of WTP for different risk reductions even if their response 

to the first valuation question is random. 

Hedonic Wage Studies

With respect to hedonic-wage studies, the White Paper describes eight selection criteria, of which four 

are based on a recently published meta-analysis by Bellavance et al. (2009). The four based on 

Bellavance et al. are listed below as criteria (5) through (8). The criteria, and the SAB’s 

recommendation regarding each criterion, are described in turn below.

(1) Use a sample size of greater than 100.

Sample size is not a significant concern for most wage-differential studies, which rely on 

large data sets of workers and actuarial risk estimates based on comprehensive fatality data. 

As noted in the discussion of stated-preference studies, sample size per se is not relevant to 

study quality or utility. Hedonic wage studies that are based on other sources (e.g., an 

original survey of workers) should be evaluated on a case-by-case basis for precision of 

estimates and representativeness of the sample.

 
17

(2) Limit selected studies to those conducted in high income countries as defined by the World 

Bank.

The SAB recommends that the EPA base its analysis only on studies conducted on U.S. 

populations. Because hedonic wage equations estimate an equilibrium outcome based on 

preferences, demographic distributions and technologies, they will be unique to each country. 

Even if incomes are similar across countries, similarity in other conditions that affect the 

revealed marginal rates of substitution between risk and wages are not assured.

(3) Omit studies based on the Society of Actuaries risk data.

The SAB agrees with this criterion. Charge Question 4a.ii. relates to this criterion and 

further comments are given in response to that charge question.

(4) Omit studies that focused on extremely dangerous jobs (e.g., police).

The SAB agrees this is a reasonable criterion because the population included in these studies 

is not representative of the population affected by EPA regulations. Should there be a case 

where the EPA is evaluating extreme risks to a well-defined population, research concerning 

the risk preferences of that population would be relevant.

(5) Retain only studies which employ a model specification “similar to that given” (ln(wi) = Xiβ 

+ φρi + μi).

The SAB disagrees with this criterion if it is applied exactly as the White Paper suggests (that 

only cross-section OLS regressions are included in the database). For example, the criterion 

would imply that estimates based on panel data, instrumental variable, or quasi-experimental 

methods would be excluded. The SAB recommends that all estimates arising from 

conceptually sound methods be included. 

(6) Exclude studies based on specific cause of death.

This criterion is appropriate when the goal is to provide an estimate of the value of reducing 

risks of workplace accidental deaths. The SAB notes, however, that the EPA should 

recognize that even within the context of accidental deaths, there is a great deal of 

heterogeneity (e.g., falls versus electrocution). The literature often aggregates these into a 

single measure of fatality risk but some new studies attempt to distinguish values by these 

risk characteristics (e.g., Scotton and Taylor 2011).

(7) Exclude studies which use the same underlying sample of workers as other studies. In other 

words, if multiple VSL estimates are reported based on the same underlying survey sample 

for stated preference studies or the same worker sample for hedonic wage studies, prior 

recommendations suggest that only one VSL estimate from a given sample be incorporated 

into the meta-analysis. 

The SAB agrees that this approach is desirable when conducting meta-analyses of clinical 

trials to describe efficacy of a treatment on a health endpoint, but it is not a desirable 

approach for meta-analyses applied to economic research. As noted above for stated 

preference studies, in economic research, multiple estimates for an outcome of interest (in 

this case, an estimate of VRR) are often reported which are based partially or wholly on 

overlapping samples. Model uncertainty, covariate-measurement uncertainty, and interest in 

heterogeneity of impacts across subpopulations all lead to varying outcome estimates. 

Rather than apply a zero weight to the information contained in all but one of the multiple 

estimates, the SAB recommends that the EPA select observations for inclusion in the metadata set or other applications based on its set of other criteria and include all estimates that 
18

meet those criteria. Including multiple estimates from the same or overlapping data raises 

issues of how to account for statistical dependence among estimates and whether a study that 

reports more estimates should contribute more to the summary measure. There are several 

methods for addressing these issues described in the meta-analysis literature (e.g., Mrozek 

and Taylor 2002, Viscusi and Aldy 2003, Bellavance et al. 2009).

(8) Exclude studies failing to report enough information to calculate the value of mortality risk 

reductions and/or the average probability of death.

The SAB agrees with this criterion.

Additional comments: 

The EPA should consider adding the following criteria:

(a) Hedonic-wage regressions should include a measure for nonfatal-injury risk, or at least 

provide evidence concerning the sensitivity of the estimated value of mortality risk to 

inclusion/exclusion of nonfatal risks. 

(b) Hedonic-wage regressions should include an appropriate level of industry and occupational 

control variables to address the problem of unobserved job characteristics that often exists in 

these studies. Panel models that control for unobserved worker characteristics do little to 

alleviate this problem when the risk variable is constructed in such a way that it varies only 

by occupation and industry of the worker. Estimates from models that convincingly address 

unobserved job and worker characteristics using the best methods available and appropriate 

for the data are preferred.

(c) Eliminate any study that relies on risk measures constructed at the industry level only (not by 

occupation within an industry), even if the source of the risk data is the Census of Fatal 

Occupational Injuries (CFOI). For example, Smith, et al. (2004) use risks that vary only by 

industry of the worker. While there has not been direct evidence of the degree to which this 

practice introduces measurement error of the type discussed by Black and Kneisner (2003) 

and Black, Galdo and Liu (2003), it would seem likely to introduce important measurement 

error.

(d) Include only estimates that are based on an appropriate sample frame or can be used to adjust 

the sample frame for the policy context. This criterion follows the suggestion for criterion 

(2) for stated preference surveys.

ii. Section 4.2.2 of the White Paper discusses problems of measurement error associated 

with some common sources of occupational risk information among other concerns 

with the hedonic wage approach. Should EPA limit its selection of hedonic wage 

studies by the source of occupational risk information? For instance, studies relying 

on data from the Society of Actuaries (SOA) have been omitted from the described 

data set. Should the SOA studies be excluded? Should other sources be excluded as 

well?

EPA should exclude hedonic-wage studies that do not use adequate risk data. The quality of the risk 

estimates is critical to wage-differential estimates of VRR and there have been substantial improvements 

in risk data over time. The SOA data are not conceptually appropriate because they include deaths from 

non-occupational risks, for which no wage differential would be expected. Prior to 1992, Bureau of 
19

Labor Statistics (BLS) workplace fatalities were survey estimates, which the National Academy of 

Sciences had questioned due to the high rate of sampling errors.5

b. Should any of the studies included in the datasets be eliminated? If so, please specify those 

studies and the reasons for eliminating them.

 

Several sources provide additional details on the difficulties with past risk estimates. Drudi (1997) 

describes problems in constructing valid risk estimates. Black, Galdo and Liu (2003) and Black and 

Kneisner (2003) provide a critique of the previous risk measures and illustrate the unreliability of study 

estimates using these measures. Leigh (1995) highlights the issue of measurement error when using risk 

data that vary only by industry or by occupation of the worker. Viscusi (2004) finds that estimates of 

the value of mortality risk using estimates of risk by industry and occupation are roughly half as large as 

estimates using estimates of risk by industry. 

Lastly, there has been a steady decline in overall numbers of workplace deaths since 1970. The labor 

force has shifted from manufacturing to service-oriented industries and exposures in the workplace have 

changed over time. Currently up to 15% of workplace deaths are homicides. The reliance on flawed 

data that are not representative of current conditions is not defensible.

In summary, all studies that rely on data of lower quality than the CFOI should be excluded.

Stated Preference Studies

The SAB prefers not to endorse or exclude specific studies. The appropriate strategy will be to consider 

the (revised) criteria recommended above and to revisit the database of studies with these criteria in 

mind.

The SAB emphasizes that the studies used should adhere to best practices. The quantities being 

estimated should correspond to a theoretically sound microeconomic construct (i.e., based on the theory 

of consumer choice) that measures an appropriate concept of value. In general, these measures will 

involve marginal rates of substitution. Ideally, this marginal rate of substitution is between a specified 

risk reduction and money, which yields an estimate of willingness to pay for that risk reduction. 

However, risk-risk tradeoffs can also be expressed as marginal rates of substitution between risks. In 

combination with appropriate studies that produce marginal rates of substitution between one of the risks

in such a pair and money, it may be possible to use risk-tradeoff information to calculate willingness to 

pay for the other risk.

Hedonic Wage Studies 

All studies not based on the U.S. workforce, not based on risk data of comparable or superior quality to 

the CFOI data, and not adhering to the other criteria discussed above should be excluded. The first two 

criteria eliminate all studies prior to Viscusi (2004). Additional criteria as discussed in response to 

charge questions 4.a. should be developed and studies after 2003 should be evaluated on these terms. 

c. Is the committee aware of relevant empirical studies in the stated preference and hedonic 

wage literatures that are not adequately captured in this review? If so, please provide 

citations.

 5 For example, the BLS estimated there to be 2,900 workplace fatalities in 1990 while the National Safety Council estimated 

10,500 and the National Institute of Occupational Safety and Health estimated 5,500 (not including Connecticut and New 

York and using only death certificates, which Drudi (1997) reports identify as few as 35% of workplace deaths).
20

There are a number of new studies that could be used to update VRR estimates using meta-analysis or 

other approaches. However, many of these are not published and therefore not peer reviewed. The 

benefits of including results from these studies are that they are likely to represent current population 

characteristics and preferences, use the most up-to-date methods in stated and revealed preference work, 

and are generally designed to elicit the values that are most policy relevant for EPA. However, these 

benefits must be weighed against the fact that the use of peer-reviewed literature has long been held as 

the gold standard of scientific credibility. Given the importance of this latter point, EPA should not rely 

on the “grey literature” (unpublished manuscripts, reports, dissertations, and other non-refereed 

materials). 

The SAB wishes to emphasize that the important aspect of peer-review that needs to be adhered to is 

peer-review of the methods, data used to fit the models, and general approach of the study. It is not 

necessary that every VRR estimate or detail of a model to be transferred in a benefits-transfer context 

appear in the peer-reviewed publication. Thus, it would be reasonable to admit VRR estimates that are 

based on methods and data that have been peer-reviewed, even if those estimates are reported only in

supplemental, unpublished reports (including working papers or dissertations). Similarly, if a study that 

estimates a WTP function has satisfied peer review, but researchers need to use parameters not reported 

in the peer-reviewed publication (e.g., the variance-covariance matrix for the parameters) in order to 

generate values for a policy-relevant context, this should also be considered to have meet the peerreview mandate.

The SAB suggests the following published studies as additional relevant empirical studies for EPA’s 

consideration. 

Other studies to consider:

Stated Preference Studies 

Cameron, DeShazo, and Stiffler (2010).

Cameron, DeShazo, and Johnson (2010).

Hedonic Wage Studies

Evans and Schaur (2010).

Evans and Smith (2006). 

4.5. Question 5 – Income Elasticities

Income elasticities are discussed briefly in section 5 of the White Paper. In keeping with Agency 

practice, we created the two databases by adjusting all estimates for income growth over time using 

an income elasticity value of 0.5 based on prior Agency reviews of the literature and results Viscusi 

and Aldy, 2003. In addition, we adjusted all estimates for inflation as well as for purchasing power 

parity where necessary, as recommended by the EEAC’s October 2007 report. Does the Committee 

agree with this approach to accounting for income growth over time? 

The question of how to adjust estimates of VRR before combining them in a meta-analysis is distinct 

from the question of how to adjust for use in policy analysis (discussed below). For meta-analysis, the 

SAB suggests that EPA not adjust VRR estimates for income growth but explore how VRR varies with

(a) the time period to which the data pertain and (b) the average sample income as part of the metaanalysis.
21

Does the Committee believe the Agency should adjust its value of income elasticity for use in policy 

analysis in light of recent findings in the literature? 

Intuition, economic theory, and empirical estimates all suggest that VRR should increase with income, 

and so EPA should adjust for changes in income in evaluating benefits of risk reduction. The income 

elasticity of VRR, like VRR itself, may vary with risk and individual characteristics. 

The literature on VSL income elasticity has employed several approaches and produced a wide range of 

results (Hammitt and Robinson 2011), including cross-section analysis of within-sample variation in 

stated-preference data (e.g., Alberini et al. 2004), meta-analysis of hedonic-wage studies (e.g., Viscusi 

and Aldy 2003), longitudinal analysis of hedonic-wage data for a particular population (e.g., Costa and 

Kahn 2004), and quantile analysis of hedonic-wage data (Evans and Schaur 2010, Kniesner et al. 2010). 

Estimates obtained from cross-section analysis of stated-preference data range between 0.1 and 1.0 

while longitudinal-study estimates range between 1.3 and 3.0. Quantile analysis yields elasticity 

estimates of 2.2 for the lowest decile of income and 1.2 for the highest decile of income. 

Consistent with its recommendations on VRR, the SAB recommends that EPA attempt to characterize 

the distribution of income elasticity and how it varies with risk and individual characteristics using one 

or more of the approaches described for characterizing VRR.

If so, what value or range of values does the Committee believe should be used? 

See previous response.

4.6. Question 6 – Statistical Approach

The White Paper describes a simplified approach for updating the Agency’s recommended 

mortality risk value estimate(s) (see section 5.1.1). This approach involves fitting a parametric 

distribution to the set of estimates from selected studies. This is similar to the approach used for 

EPA’s current default VSL estimate.

a. Should EPA pursue this approach for updating its mortality risk valuation guidance in the 

near term (until a more detailed analysis can be conducted)? 

The SAB recommends that EPA explore some of the methods proposed above (in response to charge 

question 2) for estimating a distribution of VRR for relevant cases. Whichever method is used for a 

particular application can be updated over time. If it is not possible to develop an appropriate VRR for a 

particular case within the allowable time, placeholder estimates and sensitivity analysis may have to be 

used, but if this is done, it should be made clear how the policy context differs from the contexts within

which the available WTP estimates have been measured and what assumptions are required to transfer 

benefit estimates to the policy context. 

b. If so, should the databases on which values are based be created using only one estimate 

drawn from each study or multiple estimates from each study? 

In general, it will be appropriate to include multiple estimates from each study (see response to charge 

question 4). 
22

c. If only one estimate per study should be used, what criteria should the Agency apply in 

selecting the appropriate estimate? How would these criteria vary from one segment of the 

literature to the other? The paper describes the methods used to select independent estimates 

from each study. Does the Committee agree with the methods used? 

Not relevant (see charge question 6b).

d. How important is it that estimates be drawn from non-overlapping subsamples? If multiple 

estimates per study are recommended in the construction of the meta-datasets, should the 

estimates be selected to avoid overlapping sub-samples? 

It may be appropriate to include multiple estimates from the same subsample. As discussed in response 

to charge question 4, studies of VRR often explore the effects of using alternative model specifications 

on the estimated value. When (as is often the case) it is often not clear which specification (and resulting 

estimate) is most appropriate, it is preferable to include all estimates from the same (or overlapping) 

subsets that meet other acceptance criteria. 

In other literatures, meta-analysis is sometimes used to estimate the “true” value of some physical 

parameter (e.g., Bell et al. 2005, Ito et al. 2005, Levy et al. 2005). Willingness to pay for a risk 

reduction, however, is not some fixed and immutable constant of nature; it may vary systematically with 

risk attributes such as the type of illness or injury, the latency of the illness, and the duration of 

morbidity, as well as the number of lost life-years that can be anticipated. The value of a risk reduction 

may also vary systematically with the characteristics of the individual, including age, gender, and 

income, as well as with subjective risks and other co-morbidities. Thus one sample and one model, if 

sufficiently general, can provide estimates of the values of different types of risk reductions to different 

types of people. Indeed, using one data set and a sufficiently general model to capture this heterogeneity 

can produce better estimates of how VRR varies with these characteristics by eliminating between-study 

effects.

It is also possible that the same sample can be used with different, but equally plausible, specifications 

to yield different estimates of the value of the same risk reduction. In cases where the best functional 

form is unknown and multiple alternatives yield similar measures of fit, it is appropriate to preserve 

information about both the variation across specifications in the different point estimates of the VRR as 

well as the precision (standard error) for each individual point estimate. As noted above (in response to 

charge question 4.a.i), when using multiple estimates from a single study or dataset, it is important to 

consider how to weight individual estimates and to adjust for statistical dependence among them.

e. Does the Committee still favor analyzing the stated preference and hedonic wage estimates 

separately? If so, how should the separate results of these analyses be used in evaluating new 

policies? If not, how should they be combined in a single analysis? 

The effects of risk and individual characteristics on VRR may be more important than the distinction 

between stated preference (SP) and revealed preference (RP) studies. However, wage-differential 

studies and SP studies seem to yield systematically different estimates, even for reasonably similar risks 

(e.g., traffic fatalities). The reasons for this difference are not well understood.

In evaluating how VRR varies with context, it may be necessary to distinguish SP and hedonic wage 

estimates to avoid confounding effects of risk or individual characteristics with study type. This does not 

imply that the two literatures must be treated independently. Indeed, to the extent that each literature 
23

provides useful information about the VRR in a particular context, or the variation of VRR between 

contexts, it is important to combine their results. Results from risk-tradeoff studies can also provide 

useful information and should be considered for inclusion. Although risk-tradeoffstudies do not provide

WTP estimates, they can be used to translate estimates of WTP to reduce one type of risk into WTP to 

reduce other types of risks. Of course, estimation errors would have to be compounded across these two 

stages. 

Results from hedonic-wage and SP literatures can be combined using some of the methods described in 

response to charge question 2. In addition, even though wage-risk studies may not address the types of 

illness profiles that are relevant to EPA policy contexts, these studies are vitally important for validation 

of SP studies. Hedonic-wage estimates can serve as a benchmark for evaluating stated-preference 

estimates of the value of the “sudden death in the current period” illness profile. Consistency between 

SP and best-practices RP studies, for comparable types of risks and populations, will remain an 

important criterion for cross-validation of the estimates from SP studies. (Validation is more difficult

for domains of SP studies which are not overlapped by available RP studies.)

f. Would the Committee support the development and application of separate means or ranges 

generated from the two segments of the literature? Given separate means and/or ranges from 

each segment, should the results be weighted and combined to produce a single point 

estimate or range? If so, how? Are other presentations of the results preferable? More 

generally, how should uncertainty in the estimated value(s) of mortality risk reductions be 

handled in benefits analyses? 

The use of weighted averages of individual point estimates is only appropriate if these point estimates 

measure the same thing. Recent research highlights heterogeneity in WTP for risk reductions as a 

function of both the type of risk to be reduced and the characteristics of the affected population. If 

multiple estimates are available for the same context, then these can be averaged, and it is appropriate to 

consider some sort of weighting scheme that reflects the relative precision of the different point

estimates. Weights that reflect relative precision are sometimes quantified as an inverse-standard-error 

weighting scheme, so that more precisely estimated (i.e. more certain) values are given greater weight 

than less precisely estimated values. As always, it will be important to recognize the uncertainty related 

to the choice of a statistical model as well as the uncertainty related to the standard error of the VRR 

estimate from any given statistical model.
24

4.7. Question 7 – Standardized Protocol

We are interested in developing a standardized protocol for updating the Agency’s recommended 

mortality risk value estimates on a regular basis—for example, every 5 years or so—to incorporate 

new estimates from relevant economic valuation studies as they appear in the literature. Such a 

protocol might be based on the approach outlined in Section 5.1.1 or something similar. This 

approach, combined with a set of rigorous criteria for determining which new studies and value 

estimates are suitable for inclusion in the pool for meta-analysis, would allow the Agency to update 

its guidance in a more timely and transparent manner. (After a working protocol was put in place, 

it then could be modified over time to match changes in the Agency’s general mortality risk 

valuation approach and meta-analysis methods, as necessary. See charge question 8.) Does the 

committee believe that developing such a protocol is feasible and desirable? Please explain.

The SAB believes that the Agency should establish a regular schedule for updating its value of risk 

reduction (VRR) estimates. The central-tendency estimate that the Agency currently uses is based on 

studies that are at least 20 and in some cases over 35 years old. Many of the studies included in the 

current pool may not satisfy the criteria for qualifying studies recommended by the Agency in the White 

Paper and further criteria recommended by the SAB in response to charge question 4. Moreover, the 

current estimate does not take into consideration the wealth of new studies published over the last 20 

years that make use of better techniques, better data, and that better reflect current conditions. To avoid 

using VRR estimates based on decades-old and possibly obsolete research in the future, the Agency 

should establish a protocol for updating regularly the estimates of the value of risk reduction that it uses 

in its work.

The protocol should include a procedure for updating all of the information needed to construct the 

value of risk reduction. This should include the following:

• Identification of recent additions to the literature on valuing risk reductions, particularly 

related to mortality risk, as well as studies that provide new estimates of the income elasticity 

of the value of risk reduction.

• Assessment of the quality of those studies and the estimates contained therein according to 

criteria established by the agency, as discussed above. Studies that do not meet these criteria 

should be excluded from consideration.

• The estimates of risk reduction gleaned from the set of qualified studies should be put into 

comparable real dollar terms using appropriate income elasticity and inflation adjustments.

• The procedure for combining estimates should be in line with the recommendations in 

response to charge questions 2, 6 and 8.

• All of these procedures should be adaptable to take account of new information and the 

results of new research that might enable the Agency to employ a new methodology for 

updating its VRR estimates, such as through developing and parameterizing a structural 

benefit transfer model.

Updates of the Agency’s estimates should be performed on a regular schedule in order to take advantage 

of new research as it becomes available. The exact timing of these updates will depend on the supply of 

new studies, the availability of Agency resources to devote to the task, and the nature of the review 

process for new estimates that the agency develops. The supply of research on valuing risk reductions 

has been growing in recent years as has the pace with which new studies are appearing and the Agency 

can have some influence on that supply through its research funding activities. While the supply of new 

research on this topic may be growing sufficiently fast to warrant annual updates of the VRR estimate, 

the requirements for review of new estimates produced by the Agency by the Scientific Advisory Board 
25

may make it desirable from the Agency’s perspective to update on a less frequent basis, say every 2 or 3 

years, or even 5 years at the outside. All of these update schedules are a vast improvement over prior 

practice.

Regular updates of the value of risk reduction will require an education process to make legislators, 

administration officials, and the general public aware that estimates of the values of risk reductions are 

not static. They can be expected to evolve over time as data are improved and methods are refined. 

Change in the terminology used should assist in this regard, but in conjunction with its efforts to educate 

the public about the change in terminology, EPA should also take care to inform people about its plans 

for updating these values and provide information on why this is necessary and important.

4.8. Question 8 – Benefit Function Transfer Approach

In addition to the short-term issues that underlie charge questions 1-7, we are interested in 

supporting and conducting additional research to further develop EPA’s health risk valuation 

methods over the longer-term. In particular, we would like to begin the transition from the point 

value transfer approach to a benefit function transfer approach. With this longer-term research 

and guidance development objective in mind, please answer the following questions:

a. Should EPA continue to use its current approach—that is, a point value or range of values, 

possibly with an adjustment for cancer risks—or is there now a sufficient body of empirical 

research to support the development of a more detailed form of functional benefit transfer?

As described above, the SAB recommends that EPA work toward developing a set of estimates of VRR 

for policy-relevant contexts (defined by risk and population characteristics), together with appropriate 

characterization of uncertainty about these estimates. The body of empirical research is clearly sufficient 

to estimate values for occupational accidents and may allow estimation of VRR for some other contexts 

(e.g., certain types of cancer and of respiratory or heart disease). VRR can also be distinguished by 

income and perhaps some other individual characteristics. Given the need for VRRs that differ by 

context, EPA’s Science to Achieve Results (STAR) program could be used to fill this research gap. 

b. If a functional transfer approach is feasible given the existing body of empirical results, 

should this be based on a meta-analysis or a calibrated structural preference function or 

perhaps some hybrid of these?

Alternative methods for characterizing the distribution of VRR and how it varies with risk and 

individual characteristics are discussed above (in response to charge question 2). The SAB recommends 

that EPA attempt to apply some of these approaches and evaluate the quality of the results for 

consistency with VRR estimates in particular contexts and for the plausibility of the pattern of results 

across contexts. 

Moving toward a structural preference function appears to be desirable. It would provide an integrated, 

consistent framework for understanding how individuals trade off risks against consumption and 

income. By doing so, it would provide a stronger theoretical foundation for the benefit transfer task 

commonly faced by EPA: using data on relatively well-studied risks, such as sudden accidental death, to 

infer willingness to pay for reductions in other risks. Moreover, as noted by Smith et al. (2006), a 

structural approach may allow additional data on other aspects of individual choice to be brought to bear 
26

on the problem. It may also provide a rigorous means for incorporating the results of risk-tradeoff

studies which provide valuable information but are difficult to include in traditional calculations of 

willingness to pay for risk abatement. 

Although a structural approach would provide many benefits, additional research is needed. For 

example, the existing literature has used a small number of restrictive functional forms. Before the 

structural approach will be ready for routine use, the effect of these restrictions must be investigated and 

the restrictions relaxed where possible. EPA should regard the structural approach as a high priority for 

research and an important long-term goal, but not yet as a replacement for traditional methods.

c. If the body of empirical literature is sufficient to estimate or calibrate some form of 

structural preference function, what are the key variables that should be included in such a 

function? That is, based on a priori theoretical considerations and previous empirical 

findings, which attributes of the affected individuals and the policy scenario should be 

included? What specifications are feasible given data availability?

As noted above, the theoretical and empirical literature on the structural approach is promising, but still 

at an early stage of development. The literature is not yet sufficient to estimate an authoritative model. 

As a research matter, a key initial consideration will be whether to formulate the model in terms of the 

attributes of risk (latency, morbidity, dread, etc.) or in terms of specific risks (cancer, heart disease). 

The former approach would be more versatile but the latter approach is likely to be more tractable in the 

short run. In research currently under review, for example, Cameron, DeShazo and Johnson (2010b) use 

both types of controls. Their stated preference conjoint choice study includes both the nature of the 

illness profile corresponding to a particular named health risk and the respondent’s assessment of their 

personal subjective risk of the illness in question as well as their subjective impressions of the 

controllability of that type of risk.

d. Have the econometric issues we identified (unobserved heterogeneity, heteroskedasticity, 

and small sample size) been adequately addressed by the recent meta-analyses reviewed in 

Sections 4.1.1 and 4.2.3? Would the classical approaches that we suggest for overcoming 

these data limitations improve upon previous work? If a new meta-analysis is conducted, 

what statistical approach(es) would be preferred? 

The econometric techniques that should be used in a meta-analysis will depend on the number of VRR 

estimates to be drawn from each study and the total number of observations available in the metaanalysis. For example, to be feasible, fixed effects estimators require a sufficient number of 

observations from each study. Random effects estimators assume that covariates in the model are 

uncorrelated with the error term, which may be reasonable under some circumstances but not others. 

e. What role, if any, does the Committee believe that the life-cycle consumption and mortality 

risk framework could play in evaluating health risk reductions? In particular, does the 

Committee believe that this framework could be used as a foundation for some form of 

structural benefit transfer function?

A life-cycle consumption model can be particularly useful for helping to understand how individuals 

value risk reductions at different stages of the life-cycle, which is applicable to valuing risks that are 
27

most prevalent for different ages and for evaluating effects of latency. Results of life-cycle models can 

be highly sensitive to parameters such as discount rates. Using data from stated preference and hedonic 

wage studies to parameterize a life-cycle model is an ambitious task. It faces all of the difficulties noted 

above for structural preference approach but in an even more complex form. Allowing utility functions 

to be age-dependent and to depend on risk characteristics in a manner that varies with age will be 

difficult. It is also true that the standard life-cycle model assumes people are expected utility 

maximizers, which may not be a valid assumption. Before pursuing this approach EPA should evaluate

the literature that has estimated life cycle models for the purpose of understanding savings and 

retirement decisions. An important question is how well these models have worked in that context.
28

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APPENDIX A: EPA’S CHARGE TO THE SAB

• Terminology: Replacing the term “Value of Statistical Life,” which has often been 

misunderstood as a measure of the value of individual lives, with the term “Value of Mortality 

Risk Reductions” (VMR). This change in terminology should help to avoid some of the 

confusion surrounding the interpretation of the VSL. It would not affect the results of the 

analysis itself, but rather how the benefits of reduced risks are reported and described. 

MEMORANDUM

To: Holly Stallworth, DFO

Science Advisory Board Staff Office

From: Nathalie B. Simon, Associate Director 

National Center for Environmental Economics

Date: December 16, 2010

Subject: Charge Questions for SAB-EEAC January 2011 meeting

The purpose of this memorandum is to transmit charge questions for consideration by the Science 

Advisory Board’s Environmental Economics Advisory Committee (SAB-EEAC) during our upcoming 

consultation scheduled on January 20 and 21, 2011. 

EPA and other agencies use a variety of tools, including benefit-cost analysis, to help inform regulatory 

and other public policy decisions that affect human health. When considering new regulations to 

reduce people’s exposure to pollutants, EPA first estimates how much the various options would reduce 

mortality risks. EPA then calculates the benefits associated with those options by using published 

estimates of how much people are willing to pay for small reductions in their annual risks of dying. This 

estimate is commonly known as the “Value of Statistical Life” (VSL), but it is important to understand 

that this quantity does not measure the value of an individual life. Rather, the VSL is the total 

willingness to pay for small risk reductions summed over a large number of people. This estimate, 

together with other benefits of the regulation, are then compared to the costs.

EPA is now in the process of updating its guidance for conducting benefit-cost analysis, and has 

identified a number of important issues that should be considered. These are detailed in a white paper 

on “Valuing Mortality Risk Reductions in Environmental Policy,” which will be submitted to the EPA’s 

independent Science Advisory Board shortly for review and advice. The charge questions follow from 

a white paper submitted to the SAB-EEAC for review entitled “Mortality Risk Valuation for 

Environmental Policy.” The paper addresses the following key issues: 

• Cancer Differential: Taking into account potential differences in how much people would pay for 

reductions in their chances of dying from cancer relative to other causes when estimating the 

benefits of policies that reduce exposure to cancer-causing pollutants. 
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• Altruistic Effects: Taking into account that the amount of money people would pay for “public” 

risk reductions that affect everyone (like reductions in water pollution) may differ from what 

they would be willing to pay for “private” risk reductions that only affect the individual (say, 

choosing to install a water filter in your home). Many of the published estimates of willingness 

to pay are for private risk reductions, but since EPA regulations generally result in “public” risk 

reductions, accounting for these differences when estimating benefits could be important.

As indicated in the accompanying materials, advice on these issues will not only be important ultimately 

to the revision of our Guidelines for Preparing Economic Analyses, it will be of immediate relevance to 

the Agency in its pursuit of improved guidance on mortality risk valuation in particular. We look 

forward to the SAB-EEAC’s review.

Please contact me if you have any questions about the attached charge.

Attachment

Cc: Al McGartland
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Valuing Mortality Risk Reductions for Environmental Policy

1. Current EPA guidelines and standard practice use “Value of Statistical Life” (VSL) as the metric for 

valuing mortality risks. Section 3.1 of the white paper discusses the VSL terminology commonly 

used in mortality risk valuation exercises in greater detail. The white paper suggests that the Agency 

move away from using the traditional VSL terminology in favor of a new term of art for estimates of 

the marginal rate of substitution between health risks and income (see section 3.1). Specifically, the 

white paper suggests that the Agency refer to these estimates as the “value of mortality risk,” and 

report the associated units using standard metric prefixes to indicate the size of the risk change, e.g., 

$/mr/person/yr (dollars per milli[10-3

]-risk per person per year), or $/μr/person/yr (dollars per 

micro[10-6]-risk per person per year), etc. Does the Committee agree that the Agency should pursue 

such a change? Does the Committee believe that making these changes would ease or exacerbate the 

misunderstandings documented by Cameron (2010)? Would some other terminology or approach be 

preferable? Please explain.

Experts generally agree that value function transfers can outperform point value transfers in 

cases where the characteristics of the risks and/or the exposed populations differ between the 

source studies and the policy context in measurable ways. That is, the more commodity- and 

individual-specific attributes that can be included in the benefit transfer exercise, the better the 

estimate of willingness to pay. Charge questions 2 and 3 inquire about whether applications of 

benefits transfer methods to value mortality risk reductions from environmental pollutants can be 

improved by controlling for more of the attributes that distinguish the source studies from the 

policy scenario.

2. The white paper concludes that research since the 2000 EPA Guidelines suggests that people are 

willing to pay more for mortality risk reductions that involve cancer than for risk reductions from 

accidental injury (see section 3.3). Our preliminary review suggests that a “cancer differential” of up 

to 50% over immediate accidental or “generic” risk valuation estimates may be reasonable. 

Conceptually, would the weight of evidence (both theoretical and empirical) suggest there is a

cancer differential? If so, does the Committee believe that our estimate of the differential is 

appropriate. If not, how does the Committee recommend the Agency incorporate cancer 

differentials in benefits analysis involving reduced cancer risks?

3. Environmental policies generally provide public risk reductions. However, research, particularly 

stated preference research, provides willingness to pay estimates for both public risk reductions as 

well as private risk reductions. And, some research indicates that individuals’ willingness to pay for 

public risk reductions may be different than that for private risk reductions. One factor that may 

contribute to these differences is altruism, which, all else equal, should make values for public risk 

reductions larger than those for private risk reductions. 

a. Should EPA rely on studies that estimate willingness to pay for both public and private risk 

reductions? If so, is it sufficient to control for this key characteristic in the modeling 

framework? Or, should EPA limit the analysis to studies according to the type of risk 

reduction in the study? If using only one type of study is recommended, should EPA use 

studies that estimate public or private risk reductions? If we are to limit the studies used to 

one type, is there a role for the excluded group?

b. Studies that estimate willingness to pay for public risk reductions may allow EPA to better 

capture altruistic preferences in benefit-cost analysis. Did the white paper adequately capture 
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the theory on how to incorporate altruism into the value of mortality risk reduction? How 

should altruistic preferences be treated in benefit-cost analysis? Should the Agency 

incorporate altruism into the value of mortality risk reductions, even if we are unable to 

distinguish the specific form of altruism involved (i.e., paternalistic or non-paternalistic)? 

More generally, what alternatives should the Agency pursue in the short-term to 

appropriately account for altruistic preferences when evaluating public programs, if any? 

4. The two primary literatures used to assess willingness to pay for mortality risk reductions are stated 

preference studies and hedonic wage studies. The white paper assembles two databases 

summarizing studies in both literatures, capturing much of the information outlined in number 3 of 

the SAB-EEAC’s recommendations dated October 2007 (see section 4).6

 These studies, or a subset 

thereof, would form the basis of revised guidance in the near term as well as possible future metaanalyses. 

a. The selection criteria employed in creating the two data sets are carefully outlined in the paper 

(see sections 4.1.2 and 4.2.4). Please consider these criteria in answering the following 

questions:

i. Should additional criteria be added to screen studies for inclusion in the datasets? If so, 

please specify those criteria. Should any criteria be eliminated or modified? 

ii. Section 4.2.2 of the white paper discusses problems of measurement error associated with 

some common sources of occupational risk information among other concerns with the 

hedonic wage approach. Should EPA limit its selection of hedonic wage studies by the 

source of occupational risk information? For instance, studies relying on data from the 

Society of Actuaries (SOA) have been omitted from the described data set. Should the 

SOA studies be excluded? Should other sources be excluded as well?

b. Should any of the studies included in the datasets be eliminated? If so, please specify those 

studies and the reasons for eliminating them.

c. Is the committee aware of relevant empirical studies in the stated preference and hedonic wage 

literatures that are not adequately captured in this review? If so, please provide citations.

5. Income elasticities are discussed briefly in section 5 of the white paper. In keeping with Agency 

practice, we created the two databases by adjusting all estimates for income growth over time using 

an income elasticity value of 0.5 based on prior Agency reviews of the literature and results Viscusi 

and Aldy, 2003. In addition, we adjusted all estimates for inflation as well as for purchasing power 

parity where necessary, as recommended by the EEAC’s October 2007 report. Does the Committee 

agree with this approach to accounting for income growth over time? Does the Committee believe 

the Agency should adjust its value of income elasticity for use in policy analysis in light of recent 

findings in the literature? If so, what value or range of values does the Committee believe should be 

used? 

6. The white paper describes a simplified approach for updating the Agency’s recommended mortality 

risk value estimate(s) (see section 5.1.1). This approach involves fitting a parametric distribution to 

the set of estimates from selected studies. This is similar to the approach used for EPA’s current 

default VSL estimate.

 6 The recommendations included specific features of hedonic wage and stated preference studies that should be identified in 

the studies. 
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a. Should EPA pursue this approach for updating its mortality risk valuation guidance in the near 

term (until a more detailed analysis can be conducted)?

b. If so, should the databases on which values are based be created using only one estimate drawn 

from each study or multiple estimates from each study? 

c. If only one estimate per study should be used, what criteria should the Agency apply in selecting 

the appropriate estimate? How would these criteria vary from one segment of the literature to 

the other? The paper describes the methods used to select independent estimates from each 

study. Does the Committee agree with the methods used? 

d. How important is it that estimates be drawn from non-overlapping subsamples? If multiple 

estimates per study are recommended in the construction of the meta-datasets, should the 

estimates be selected to avoid overlapping sub-samples?

e. Does the Committee still favor analyzing the stated preference and hedonic wage estimates 

separately? If so, how should the separate results of these analyses be used in evaluating new 

policies? If not, how should they be combined in a single analysis? 

f. Would the Committee support the development and application of separate means or ranges 

generated from the two segments of the literature? Given separate means and/or ranges from 

each segment, should the results be weighted and combined to produce a single point estimate or 

range? If so, how? Are other presentations of the results preferable? More generally, how 

should uncertainty in the estimated value(s) of mortality risk reductions be handled in benefits 

analyses?

7. We are interested in developing a standardized protocol for updating the Agency’s recommended 

mortality risk value estimates on a regular basis—for example, every 5 years or so—to incorporate 

new estimates from relevant economic valuation studies as they appear in the literature. Such a 

protocol might be based on the approach outlined in Section 5.1.1 or something similar. This 

approach, combined with a set of rigorous criteria for determining which new studies and value 

estimates are suitable for inclusion in the pool for meta-analysis, would allow the Agency to update 

its guidance in a more timely and transparent manner. (After a working protocol was put in place, it 

then could be modified over time to match changes in the Agency’s general mortality risk valuation 

approach and meta-analysis methods, as necessary. See charge question 8.) Does the committee 

believe that developing such a protocol is feasible and desirable? Please explain.

8. In addition to the short-term issues that underlie charge questions 1-7, we are interested in 

supporting and conducting additional research to further develop EPA’s health risk valuation 

methods over the longer-term. In particular, we would like to begin the transition from the point 

value transfer approach to a benefit function transfer approach. With this longer-term research and 

guidance development objective in mind, please answer the following questions:

a. Should EPA continue to use its current approach—that is, a point value or range of values, 

possibly with an adjustment for cancer risks—or is there now a sufficient body of empirical 

research to support the development of a more detailed form of functional benefit transfer?
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b. If a functional transfer approach is feasible given the existing body of empirical results, should 

this be based on a meta-analysis or a calibrated structural preference function or perhaps some 

hybrid of these?

c. If the body of empirical literature is sufficient to estimate or calibrate some form of structural 

preference function, what are the key variables that should be included in such a function? That 

is, based on a priori theoretical considerations and previous empirical findings, which attributes 

of the affected individuals and the policy scenario should be included? What specifications are 

feasible given data availability?

d. Have the econometric issues we identified (unobserved heterogeneity, heteroskedasticity, and 

small sample size) been adequately addressed by the recent meta-analyses reviewed in Sections 

4.1.1 and 4.2.3? Would the classical approaches that we suggest for overcoming these data 

limitations improve upon previous work? If a new meta-analysis is conducted, what statistical 

approach(es) would be preferred? 

e. What role, if any, does the Committee believe that the life-cycle consumption and mortality risk 

framework could play in evaluating health risk reductions? In particular, does the Committee 

believe that this framework could be used as a foundation for some form of structural benefit 

transfer function?