Transcript Measuring Disability in a Survey or Census Context: Parallel Work Advancing the Field Barbara M.

Measuring Disability in a
Survey or Census Context:
Parallel Work Advancing the
Field
Barbara M. Altman, Ph.D.
Disability Statistics Consultant
Active Measurement Efforts
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Washington Group – Measurement on an
international level
ISDS – Federal efforts to prepare for improved
data collection
ACS – Development of improved questions for
Census Survey
Measurement Issues
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Issue 1 - Addressing the problems of the wide
ranging variety of questions and wording.
Issue 2 – Understanding the nature of the conceptual
model serving as a basis for definition and
measurement. For example, a theoretical or
legislative model.
Issue 3 – How does the purpose of data collection
dictate the way the conceptual element from the
model is operationally defined?
Issue 4 - Is the measurement of a ‘true’ population
feasible or desirable? Is there “one” true number?
The Washington Group on
Disability Statistics
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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
individual country use and for international
comparisons
The Washington Group was set up to:
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Foster international cooperation in the area of
health and disability statistics
Develop disability measures suitable for censuses
and surveys that will provide basic information on
disability
Untangle the web of confusing and conflicting
disability estimates
Washington Group: Objectives
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Develop a small set/s of general disability
measures for use in Censuses
Recommend extended set/s of items to
measure disability as components of
population surveys / supplements
Address methodological issues associated with
disability measurement
Current International and National
Situation
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Currently national censuses in developing
countries use one of three types of questions
that provide widely differing estimates of
national prevalence of disability:
The three types of questions include:
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Generic question 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
Current problems nationally
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Question domains and wording varied across surveys and
census –ability to crosswalk surveys limited
Many questions in use predate improved theoretical
approaches
Moving from Concept to Definition to
Measurement: The Conceptual Model
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A conceptual model of the key components
and their relationship is a basic tool for
developing or selecting questions.
WG selected the ICF as the conceptual model:
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Common point of reference
Provides a common vocabulary, classifies
domains within conceptual areas
Does not provide an operational definition or a
way to measure the concepts
Moving from Concept to Definition to
Measurement: The Definitional Paradox
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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 operational definition to use
Need to understand the choices that are being made when a
purpose and an operational definition are chosen
Need to understand the choices that are being made when
time, expenses and respondent burden limit number of
questions
Purpose of Data Collection
3 major classes of purposes at aggregate level
 Service Provision
 Monitoring functioning in the population
 Assess equalization of opportunities
2 criteria for selection of a purpose
 Relevance—particularly for policy makers
and program officials
 Feasibility
Purpose: Service provision
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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
Purpose: Monitoring functioning in the
population
•
all those with
activity or
participation
limitation
Response
comparability
problematic since
participation is
culturally and
environmentally
determined
Population reporting work limitation
25
Proportion (%)
• Seeks to identify
20
15
10
5
0
2005
2010
2015
2020
2025
Purpose: Equalization of opportunities
• Seeks to identify
•
90
Proportion (%)
all those at
greater risk than
the general
population for
limitations in
activity or
participation
Disability as a
demographic
% Employed
60
30
0
Nondisabled
Disabled
Issue 4 –What Population?
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Actually, if we identify disability as an outcome of
the person’s interaction with his/her environment we
are seeking to identify a person with a Greater Risk
of Disability based on health related functional
limitations
The Population would be defined as: persons with
functional limitations who are at risk for the loss
or restriction of opportunities to take part in the
normal life of the community on an equal level
with others due to physical, social and other
environmental barriers.*
*Adapted from Scott Brown’s
presentation at the ISDS Meeting
Locating Risk in the ICF Model
Health Condition
?
Body Functions &
Structure
Participation
Environmental
Factors
Source: ICF, WHO, 2001
Personal
Factors
THE ‘At Risk’ POPULATION: In
Pure ICF Terms
Body Functions
&
Structures
Activities
&
Participation
Environmental
Factors
Functions
Capacity
Barriers
Structures
Performance
Facilitators
ICF Components
Moving from Concept to Definition to
Measurement: Measurement of
equalization of opportunities
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Locate the definition of disability at the most
basic level of activity/participation in core
domains
This level is associated with the ability or
inability to carry out basic bodily operations
at the level of the whole person (i.e. walking,
climbing stairs, lifting packages, seeing a
friend across the room)
Criteria for inclusion of domains
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Suitability for self-report
Parsimony
Validity across various methodological modes
WG Perspective – Cross cultural comparability
Possible domains that fulfill these criteria:
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Walking
Seeing
Hearing
Cognition
Benefits of this approach
 Development of a demographic means of
understanding disability (can compare
persons with and without disability)
 Connection between disability and
participation can be made during data
analysis
 Effectiveness of programs / policies to
promote full participation can be monitored
Intended use of data
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Compare levels of participation in employment,
education, or family life for those with disability
versus those without disability to see if persons
with disability have achieved social inclusion
Monitor prevalence trends for persons with
limitations in specific basic activity domains
Measurement Answers*
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Issue 1 - Addressing the problems of the wide ranging variety
of questions and wording.
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For international comparability we have found it necessary to locate
our population of interest within the basic levels of functioning of the
whole person. If we want comparability within the US across surveys it
is essential to have a similar basic standardized operational measure.
Issue 2 – Nature of the conceptual model serving as a basis for
definition and measurement. For example, a theoretical or
legislative definition.
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Commonly accepted theoretical approaches need to underlie the
conceptualization of the components of disability that are then
operationalized. Legislative definitions need to be treated as “purpose”
of data collection since the varieties of legislation and legislative
definitions are directed at specific policy purposes.
*Personal Opinion
Measurement Answers*
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Issue 3 - Purpose of data collection effort may dictate the
conceptual component from the model as well as the specific
operational definition of disability.
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Major disconnect occurs between data collection process, use and
interpretation. While we can push for purpose related
operationalization, how the measures are used in analysis requires
careful planning and interpretation and understanding of the limitations
of the measures.
Issue 4 - Is the measurement of a ‘true’ population feasible or
desirable? Is there “one” true number?
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We can’t represent the ‘true’ population but we can represent a
consistent population by using a standardized subset of questions across
surveys (or across countries). That is both feasible and desirable and
does not preclude inclusion of other measures for specific purposes.
*Personal Opinion