1. The Definition and Measurement of Disability
The Work of the Washington Group on Disability Statistics
Jennifer H. Madans
National Center for Health Statistics, USA
for the Washington Group on Disability Statistics
April 17

2. This presentation will cover:
Disability definition and the International Classification of Functioning, Disability and Health – ICF
Disability measurement and the Washington Group on Disability Statistics – WG
April 17

3. The Washington Group on Disability Statistics (WG)
In June of 2001, the UN International Seminar on the Measurement of Disability recommended the development of principles and standard forms for global indicators of disability to be used in censuses
There was a broad consensus on the need for population based measures of disability for country use and for international comparisons
Problems connected with the concept “Disability” are found in: defining exactly what should be measured; developing the content of questionnaires; developing the techniques of interviewing; training interviewers; participating to work out good methodology internationally
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4. Global disability prevalence rates*
High-income countries
Low-income countries
Year %
Canada
1991
14.7
Kenya
1989
0.7
Germany
1992
8.4
Namibia
3.1
Italy
1994
5.0
Nigeria
0.5
Netherlands
1986
11.6
Senegal
1988
1.1
Norway
1995
17.8
South Africa
1980
Sweden
12.1
Zambia
1990
0.9
Spain
15.0 UK
12.2
Zimbabwe
1997
1.9
USA
Malawi
1983
2.9
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* Sources and methodologies are country specific

5. The WG was created to:
Foster international cooperation in the area of health and disability statistics
Untangle the web of confusing and conflicting disability estimates
Develop a small set of general disability measures suitable for use on Censuses
Develop extended set/s of items to measure disability on population surveys
Address methodological issues associated with disability measurement
Current Problem:
Censuses use different types of questions that provide widely differing estimates of national prevalence of disability.
Types of questions include:
Generic questions about the presence of a condition
Generic questions about the presence in the household of a person with a disability followed by a list of impairments
Checklist of impairments
Questions on functional domains
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6. Our understanding of disability has changed:
from:
a medical definition – based on a medical condition as an individual pathology
to:
a concept based on the consequences of diseases - on functional capacity and/or social participation
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7. Moving from Concept to Definition to Measurement:
The Conceptual Model
ICF selected as the conceptual model:
Common point of reference
Common vocabulary
Does NOT provide an operational definition or a way to measure the concepts
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8. Structure (Impairment)
The ICF Model
Health Condition
(disorder/disease)
Body Function &
Structure (Impairment)
Activities
(Limitation)
Participation
(Restriction)
Environmental
Factors
Personal
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Source: World Health Organization, 2001

9. Moving from Concept to Definition to Measurement:
The Definitional Paradox
There is no single operational definition of disability
Different operational definitions lead to different estimates
The question you are trying to answer (the purpose) will determine which definition to use
Source of data can impact choice of purpose and definition
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10. Purpose of Data Collection
3 major classes of purposes at aggregate level:
Service provision
Monitoring functioning in the population
Assess equalization of opportunities/ participation
2 criteria for selection of a purpose:
Relevance - particularly for policy makers and program officials
Feasibility - especially for international comparability
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11. Purpose: Service provision
Seeks to identify those with specific needs, usually the most serious problems
Requires detailed information about the person and the environment
Influenced by the organization and structure of service organizations within a particular culture
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12. Needs assessment/service provision
Benefit eligibility
Income support / social security
Subsidies
Device manufacture
Formal rehabilitation services
Education programs
Medical rehabilitation
Vocation rehabilitation
Personal assistant services
Advocacy services
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13. Purpose: Monitoring functioning in the population
Seeks to identify all those with activity limitations or participation restrictions due to ‘health’ – e.g. ‘are you limited in the work you can do because of a health problem?’
Difficult to craft questions
Response comparability is problematic since participation is culturally and environmentally determined
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14. Example: Monitoring trends in functioning
Population reporting limitation in work
Information is used to characterize population functioning
Focus on the interaction of people and environment

15. Purpose: Equalization of opportunities
Seeks to identify all those at greater risk than the general population of experiencing restrictions in social participation, for example in employment, education or civic life
Disability as a demographic
Civil rights definition
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16. UN Convention on the Rights of Persons with Disabilities?
UN Convention (2006): Persons with disabilities include those who have long-term physical, mental, intellectual or sensory impairments which in interaction with various barriers may hinder their full and effective participation in society on an equal basis with others.
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17. Moving from Concept to Definition to Measurement:
Measurement of equalization of opportunities
Locate the definition of disability at the most basic level of activity in core domains
Defined as the ability or inability to carry out basic actions at the level of the whole person (i.e. walking, climbing stairs, lifting packages, seeing a friend across the room)
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18. Moving from Concept to Definition to Measurement:
Measurement of equalization of opportunities
Measure functioning that defines disability status without accommodations to the extent possible (e.g., use of assistive devices, personal assistance)
Participation outcomes are measured with accommodations (e.g., are you employed)
Connection between ‘disability’ and participation is made during data analysis
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19. Structure (Impairment)
Locating Risk in the ICF Model
Health Condition
(disorder/disease)
Body Function &
Structure (Impairment)
Participation
(Restriction)
Environmental
Factors
Personal ?
ACTIVITY
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Source: World Health Organization, 2001

20. Example: Equalization of opportunities
Compares actual participation by level of risk for limitations in activity or participation
Disability used as a demographic
% Employed

21. Criteria for inclusion of domains
Cross cultural comparability
Suitability for self-report
Parsimonious
Validity across various methodological modes
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22. Possible question options
Mobility
Walking
Climbing stairs
Bending or stooping
Reaching or lifting
Using hands
Sensory
Seeing
Hearing
Communicating
Understanding
Speaking
Cognitive functions
Learning
Remembering
Making decisions
Concentrating
Emotional functioning
Interpersonal interactions
Psychological well-being
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23. WG short set of questions for censuses:
Because of a Health problem:
Do you have difficulty seeing even if wearing glasses?
Do you have difficulty hearing even if using a hearing aid?
Do you have difficulty walking or climbing stairs?
Do you have difficulty remembering or concentrating?
Do you have difficulty with (self-care such as) washing all over or dressing?
Using your usual (customary) language, do you have difficulty communicating (for example understanding or being understood by others)?
Response categories:
No - no difficulty; Yes - some difficulty;
Yes - a lot of difficulty; Cannot do at all
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24. What do we end up with?
Identify persons with similar types and degree of limitations in basic actions regardless of nationality or culture
Represent the majority (but not all) persons with limitations in basic actions in any one nation—no psychological or upper body functioning
Represent commonly occurring limitations in domains that can be captured in the Census context
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25. Intended use of data
Compare levels of participation in employment, education, or family/social life for those with disability versus those without disability to see if persons with disability have achieved social inclusion
Monitor effectiveness of programs / policies to promote full participation can be monitored – UN Convention
Monitor prevalence trends for persons with limitations in specific basic activity domains
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26. Limitations
One set of measures will not satisfy the multiple needs for disability data
Excluded populations:
very young children
institutionalized population
homeless
floating populations
It is not our purpose to:
identify every person with a disability within every community
replicate a population evaluated across a wider range of domains that would be possible with other forms of data collection – extended set
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27. Work on Extended Measures
The WG is developing an extended set of questions that:
goes into greater depth on the same 6 domains covered by the short set of questions, and
includes additional domains of functioning such as learning, affect, pain and fatigue,
includes questions about age at onset and impact of the difficulty,
is currently being cognitively tested in preparation for subsequent field testing.
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28. April 17