Disability World
A bimonthly web-zine of international disability news and views, Issue no. 7 March-April 2001

International News and Views:

Measuring the Quality of Life: Rethinking the World Bank's Disability Adjusted Life Years

By Nora Ellen Groce, Ph.D., Yale School of Public Health (nora.groce@yale.edu)
Mary Chamie, Ph.D., Officer in Charge, Statistics Division, United Nations
Angela Me, Ph.D., Statistics Division, United Nations

Over the past two decades, enormous strides have been made in the arena of disability rights.  Major initiatives, culminating in the United Nations International Decade of the Disabled, and a flurry of progressive legislation and new programs around the world have fostered critical rethinking about the nature of disability and society.
Unfortunately, some sectors of the world's health and development community remain unaware of this large and significant social and political movement.  A striking example first appeared in the 1993 World Bank's World Development Report. As part of an effort to prioritize health needs by quantifying the global burden of disease, health economists working in conjunction with the World Bank developed "Disability Adjusted Life Years" (DALYs), a statistical measurement for the value of lives lived with a disability. This method of measurement defines "disability" in a way that is strikingly at odds with the social, economic and human rights gains that have been made by the disability community around the world.

What is a DALY?

DALYs assume a "reduced value" of lives lived with a disability.

The first calculation of the DALY appeared in the 1993 World Development Report (The World Bank, 1993) and in  1996 joint effort by WHO, World Bank and the Harvard School of Public Health produced The Global Burden of Disease (Murry and Lopez, 1996) in which DALY methodology and findings were presented in more detail.

The primary focus of the DALY is to measure the impact of diseases in terms of years of burden and loss. The burden produced by a certain condition/disease is defined as the sum of two components: years lived with disability and years of life lost from premature death. We do not argue with the importance of estimating the outcomes of disease. However, the authors of the DALY have conceptualized and measured disability in a way that is dangerously out of step with current thinking about what constitutes a disability and what individuals with a disability have to contribute to society.

Over the past two decades, concepts of disability and society have moved out of the shadow of medicine and away from models that relied on able-bodied people's charity. Disability has been increasingly reframed as an issue of social entitlement, economic opportunity and human rights (United Nations Commission on Human Rights, 1991, United Nations 1993). Unfortunately, the current attempts to link disability with disease found in the new DALY methodology pushes the debate back to the outdated medical model of disability.  The fact that DALYs are being designed as a tool to aid in policy decisions and resource allocation makes it of particular concern.

Disability-Adjusted Life Years

Defining Disability-Adjusted Life years as "a unit used for measuring both the global burden of disease and the effectiveness of health interventions," (World Bank Report, 1993), the DALYs calculate the present values of future years of life lost for individuals who either die or become disabled.  Without actually defining "disability", those working on the Global Burden of Disease methodology use the term disability interchangeably with ill-health, and assume that living with a disability represents a net drain on society. Indeed, in explaining the need for using DALYs calculations rather than mortality figures, the World Bank Report states:

"...  problems are often assessed in terms of mortality, but that indicator fails to account for the losses that occur this side of death because of handicap, pain or other disability.  A background study for this Report undertaken jointly with the WHO, measures the global burden of disease by combining (a) losses from premature death, which is defined as the differences between actual age at death and life expectancy at that age in a low-mortality population, and (b) loss of healthy life resulting from disability.  The GBD is measured in units of disability-adjusted life years (DALYs)."
- World Bank Report:1993:25

The Report unquestioningly links disability with ill-health, and assumes that individuals with a disability lie somewhere between life and premature death.

Quantifying Disability

In order to quantify disability in terms of human potential, selected groups of physicians who work on illness prevention were asked to list diseases known to cause disability and to estimate disability incidence for specified countries and areas. Estimates were then made to reflect the assumed quality of remaining years of life with persons with disabilities resulting from these specific diseases.  The final Disability-Adjusted Life Years were determined by the scoring of a panel of medical experts.

Six classes of severity of disability were identified and described, ranging between "perfect health and death" (Murray, 1994 p. 12), and were ranked by the physicians and economists according to expected limitations of one's ability "to perform recreation, education, procreation or occupation," as well as potential "need for assistance with instrumental activities of daily living such as preparing meals, shopping or housework" and the "need for assistance with eating, personal hygiene or toilet use."  Because data were limited on this subject, these needs are also "assumed," based upon physician opinion and understanding of disease.

The charge given to the medical experts was to provide their professional opinion on the severity of disability associated with each particular disease and/or impairment as noted above.  Six classes of severity of disability were established.  Then each of 109 diseases were assigned by professional opinion to one of these six classes of severity.  This meant that a variety of diseases and impairments believed by the expert judges to be of equal disability severity were placed together in one of the six classes (blindness and paralysis for example, were in the same class of disability severity).

The classes of disability severity were assigned weights ranging from zero, representing perfect health or no disability, to one, representing the most severe disability, or death. Experts then voted on the weight, from Zero to One, to be assigned to each of the six classes. The numerical average obtained through this vote was then assigned to all the diseases grouped together in that particular class of disability severity. The medical experts were asked to consider the likely incidence, age of onset, gender and duration of disability that they believed to be associated with each specific disease.  These estimates were based on scattered data that had been collected through community-based epidemiological research, knowledge of routine information from health facilities and through "expert judgment" of physicians and other scientists involved in the prevention of disease (World Bank Report:1993, p. 214).

The DALY was obtained by multiplying the expected duration of the condition (to remission or to death) by a severity weight that judged the severity of the disability believed to be associated with the 109 diseases, in comparison with loss of life. For example, class 2, which includes most cases of leprosy and half the cases of pelvic inflammatory diseases, was judged to have a disability severity weight of 0.22, and class 4, which includes 30% of cases of dementia and 50% of those of blindness, were assigned a severity weight of 0.6. The death and disability losses were then combined and allowance was made for a discounted rate of 3 percent (valuing future years of healthy life at progressively lower levels) and for age weights (so that years of life expected to be lost at different ages were given different relative values).

Definitional Concerns

There are a number of specific methodological issues that might be raised in any critique of the DALYs.  However, here we are more concerned with the fundamental assumption about the nature of disability that undergird the DALYs.

To begin, although the DALY provides extensive discussion of disability, disability is itself, never defined. Indeed, the methodology was derived by grouping together a wide range of serious diseases according to their expected physical, sensory, intellectual and emotional consequences. Scientific research and the review of the literature was bypassed for the more expedient approach of assuming the associations based upon medical expert opinion.

Disability is not an Illness

A further problem with the DALYs is the assumption that disability is an illness.  Years of life lived with disability are not necessarily "lost" years, nor can they always correctly be described as years "burdened" by disease. According to the World Health Organization, disability is not an illness. Equating disability with illness has led to confusion as is evident in the DALYS, where researchers attempt to classify disability states based upon the International Statistical Classification of Diseases (WHO, 1992).

Indeed, most individuals experiencing disability are not continually in need of medical care, nor are they continually too ill to function.  Becoming disabled can occur at any point in the life span and the majority of individuals with a disability will live for years with little or no medical assistance. For most, the bulk of their life-span will be lived outside the province of the medical sector. Their lot in life will be considerably more comfortable and productive if they have access to resources and technical aids - such as hearing aids, eye glasses, wheelchairs, or environmental or architectural changes, such as ramps, grab bars and large print newspapers, that will allow  them more independence and self-sufficiency. But these individuals will not simply disappear should these resources not be forthcoming.


Another fundamental concern is that the DALYs are, by their very nature, subjective.  It is sobering to note that, to the best of our knowledge, not one of the medical experts at the meeting in which severity was determined represented an organization of persons with disability. In this day and age, it is difficult to imagine an international forum on women's health being assembled without some input from women's groups. A discussion of Fourth World peoples would almost certainly include some representatives from such ethnic and minority populations. This lack of inclusion is all the more problematic because a growing body of research has found that able-bodied people are more likely to assign a poorer quality of life to living with a disability than do those who actually live with a disability.  (Baker:1993; Bellisari:1993; Shaw:1994).

Studies have also found that able-bodied medical professionals who deal with disability, the very experts who were asked to assess the quality of life with disablement, are particularly likely to see the whole of an individuals' life in terms of medical needs rather than seeing health care or rehabilitation to be one component of a fuller life (Makas:1993).

Disability in Society

The social and economic implications of living with a disability constitute an equally significant point left unanswered by the Disability-Adjusted Life Years scale. The past two decades have brought a growing realization that the quality and achievement associated with an individual's life depend in large measure on the socio-cultural, legal and economic ramifications of living with a disability (Werner:1989; WHO/ICIDH:1993).

Indeed, the UN World Program of Action clearly states that the quality of life with disability reflects the interrelationship between an individual and his or her environment. The United Nations Standard Rules on the Equalization of Opportunities for Persons with Disabilities and the United Nations Decade on Disability, focused its attention primarily on the social, economic and legal barriers societies put in the way of living with a disability (United Nations, 1982,1993).

The WHO's International Classification of Impairments, Disabilities and Handicaps (ICIDH) has endeavored to more accurately define disability by emphasizing the social context within which individuals must live.  The DALYs are unable to address disability in a context wider than that of the individual. For example, using the ICIDH model, a spinal cord injury resulting in paraplegia  may prove far more "handicapping", both socially and economically, to a sugar cane cutter than to a college professor.  The identical loss of sight for an impoverished washerwoman living in a shanty town and a wealthy urban woman might produce very different ramifications; indeed the second woman's need for assistance in home or career may create jobs for one or more individuals.  According to the DALYS, both men with paraplegia and both women with severe vision loss would be equally burdensome to their societies - but in the real world, the issues that affect their lives are economic and social, not medical.

A Cross-Cultural Perspective

The social subjectivity of the procedure for valuing disability in the Disability-Adjusted Life Years scale becomes even more complex when viewed from a cross-cultural perspective. Whereas the standardization of measurement of the disability itself has been shown to be possible cross-culturally, it has been shown that the value attached to any disability state varies markedly between cultures   (Groce and Zola:1993; Mallory:1990).

For example, how can one use the DALY to quantify the value of disability for an individual with a slight disability, such as walking with a limp, in a society where such a disability would make it difficult to marry and unmarried adults are not allowed to fully participate in the community? (Whyte and Ingstad:1995). How significant is profound deafness if enough hearing individuals use sign language to allow easy communication? (Groce:1985).

Moreover, ideas about the causes and consequences of disability are often embedded in specific cultural belief systems (Detwyler:1991; Scheer and Groce: 1988). In countries with a number of distinct cultural groups, the weighing system of the quality of life with disability for DALYs would need to be adjusted for each distinct ethnic or tribal group.

Prevention versus Inclusion

Inherent in the DALY calculation is the assumption that the DALY is to be a "decision making tool to be used by health administrators to effectively select health interventions for public financing" (World Bank Report:1993:34). According to DALYS, priority must be given to the prevention of diseases that can be treated most easily and inexpensively.  Diseases which are more rare or which require more expensive interventions receive a lower priority.  Far down on such a list is rehabilitation and services for those who already have a disability.

In arguing against the DALYs, it is easy -and misguided- to be drawn into an argument between funding prevention versus funding rehabilitation and inclusion.  We are not arguing against low-cost, effective measures that prevent avoidable disability.  However, even if most health care dollars were poured into prevention, there would continue to be a certain percentage of all populations who would be born or become disabled.  Some causes of disability can be prevented, but only at high costs in terms of the health care dollar, for example, effective perinatal care or the improvement of roads.  Other disabilities are eminently preventable, such as those resulting from poverty, malnourishment and the use of land mines, but we lack the public will to address them.

Finally, even if the leading causes of disability were eliminated, those individuals already affected by them would still need services and resources. Indeed, advances in medicine insure that a rising number of individuals with significant impairments will survive who would not have done so even a decade ago - and these individuals may live with a far higher degree of disability than was the case only recently. The improvement in survival rates among people experiencing quadriplegia and those with severe head trauma are examples. In the final analysis, the issue is not to create a tug of war between funds for prevention and funds for rehabilitation and inclusion. The issue is the extent to which investment of resources - education, job-training, inclusion and civil and legal rights - will yield an improved quality of life and improve the participation of those who experience disability.  In terms of potential productivity, calculating a DALY score to assess quality of life probably tells us far less about what it is like to live with a disability than statistics such as UNESCO's estimate of the remarkably low literacy rates for individuals with disability world wide (United Nations, 1990).  Most individuals with a disability do not die if they do not receive rehabilitation or assistance. However, their capacity to make productive contributions to their families and to society may be significantly diminished.

Prioritizing needs in terms of available resources is not, in itself, a useless exercise. It would be significant if one component of the DALYs were to assess what programs for those with disability could reach the greatest numbers at the lowest costs. For example, it might be argued that a community-based program promoting inclusion and self-sufficiency for  people with mobility impairments is far more cost effective than a program to build expensive, high tech rehabilitation facilities. Unfortunately, the DALY scale does not permit such comparisons. The use of DALYs assumes that once disabled, one can only wait passively for assistance from others, since the scale leans towards ranking disability as a component of "partial death" rather than as an assessment of the potential for "quality of life."


The Disability-Adjusted Life Years scale is an attempt to rank international health imperatives that does a significant disservice to individuals with disability, primarily owing to the questionable use of a value-laden weighing scheme for assessing the value of "years of life lost" with disability. The underlying assumption in the DALYS is that individuals with disability are a net drain on society. There is no alternative weighing mechanism in the DALY that would allow us to measure positive contributions to society made by individuals with disabilities.  According to the DALY scheme, the years that Franklin D. Roosevelt spent as president of the United States, were years of "life lost" to disability, as are the many years that astrophysicist Stephen Hawking has spent teaching and writing. DALYs only allow calculation  of deficits incurred by the very existence of the disability itself. Although DALYs may help economists and ethicists distribute health care to the masses, we fear that it may also allow them to more easily justify the disenfranchisement of an entire segment of humanity.

Using specific medical diagnosis as a proxy for the entire life experience, the DALYs calculation can be used to justify the denial to disabled populations not only of medical resources, but of resources from all other sectors of society as well. A person's inability to walk or to see should not make him or her less worthy to receive an education, a training or a trade, housing or food.  The DALYS  could be used to deny individuals with disability the very assistance they will need to make their lives fuller and to contribute to their societies.  To then assume that this group is a drain on society becomes a self-fulfilling prophecy.

A basic premise of the DALYs is the argument that maintaining the health of populations has a significant financial benefit. In the World Bank Report, the authors set aside a chapter to argue "Why Health Matters."  They state, "the most obvious gain are fewer work days lost to illness, increased productivity, greater opportunities to obtain better-paying jobs and longer working lives. ...Healthier workers earn more because...they can be more productive and can get better-paying jobs."  (World Development Report:1993:18).  We do not disagree with this, but see no reason why it is not equally applicable to disabled individuals whose health is maintained and whose social and economic options expanded.

It is not the intention of this paper to discourage further scientific assessment and measurement of disability. Unfortunately however, the DALY methodology does not take advantage of recent work in the field of disability. It also ignores the documented necessity of using international standards and classifications which help assess disability through careful measurement. (Rodriquez: 1989; Chamie: 1994)

The United Nations and the World Health Organization have time and again come forward to advocate greater civil and human rights for disabled populations world wide. Very recently, a UN Resolution was adopted which asked the United Nations Development Program to include an evaluation of the way a society treats its disabled citizens as a factor in the quality of life of that society. The approach of the General Assembly underscores the fact that life with disability need not be viewed necessarily as "lost years." We commend such efforts, and feel that they may prove to be viable models upon which those promoting DALYs needs to reflect.

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