1. 11/19/2014 “Perceived” severity reported by individuals and “actual” disability as measured by clinical testing Washington Group on Disability Statistics

2. 11/19/2014 Sources of Data on Disability National Censuses population census to obtain prevalence rates as a screening question for a follow-up study Surveys extended questions on a health or specialised disability survey Other population survey Clinical/Administrative records Registries Medical and/or insurance records Performance measures

3. 11/19/2014 Population Censuses Principal source of statistics on a population and its characteristics A nation wide activity with every person enumerated (universal enumeration) Provides important information on demographic profile economic and social data

4. 11/19/2014 CENSUS - Advantages Data can be tabulated for small, local areas Prevalence rates can be calculated Detailed descriptive cross-tabulations are not subject to sampling errors. If disability questions remain comparable, they can be useful for time-series analysis of disability rates. Can provide useful sampling frame for research on persons with disability Comparisons can be made between people with and without disability

5. 11/19/2014 CENSUS - Limitations Limited to basic socio-economic and demographic characteristics. Limited range and depth on special situation of disabled persons - disability has low priority. Only short/simple questions can be included. Data collection is infrequent. Time lag between data collection and dissemination. Institutionalized population may be left out. Very costly and time consuming. Enumerators may be limited in amount of training on disability. Census completed by one person for the household, who may not have full information on the disability status of others.

6. 11/19/2014 Surveys are not intended to enumerate every household or individual are designed to be representative of the population most are household based, but it is important to include the institutional population disability data are collected through: special disability survey module on disability in another survey

7. 11/19/2014 SURVEYS - Advantages Flexibility in the depth and range of topics that may be covered. Relatively easy to initiate, given the ability of a sampling frame and survey-taking infrastructure. Greater control over the conditions of observation and the interview. Design modifications may be tried to increase the power of the survey. Greater opportunity for supervision of fieldwork and pre-testing of detailed questions about disability. Measurement can be built in e.g. eye tests or manual dexterity.

8. 11/19/2014 SURVEYS - Limitations Limited ability to analyse prevalence rates for local areas due to limited sample size and subsequent sampling errors. A very large sample size is required to capture an adequate number of persons identified as having a disability. Coverage of populations in unusual circumstances is typically very poor e.g. the institutionalised, the homeless, refugees, nomadic populations etc.

9. 11/19/2014 CLINICAL/ADMINISTRATIVE/ PERFORMANCE Data Advantages: Access to very detailed medical data Assessment of ‘true’ capacity environment free

10. 11/19/2014 CLINICAL/ADMINISTRATIVE/ PERFORMANCE Data Limitations: Not available in many countries Coverage of population may be selective and limited Coverage is governed by programmatic definitions Comparability of data is problematic since data are specific to country and context

11. 11/19/2014 Considerations: Administrative systems based on clinical evaluation Some limitations of body functions and structure can be measured through administrative registers These tend to be associated with specific diagnoses impairments that ‘trigger’ the social security system impairments that are more severe in nature.

12. 11/19/2014 Considerations: Administrative systems based on clinical evaluation Activity limitations and participation restrictions can more accurately be measured through population-based methods (household surveys and population censuses) Can assess the individual’s functioning as a whole person, as opposed to the function and structure of his/her body parts

13. 11/19/2014 Considerations: Performance measures Evaluates specific and limited functions in a standard environment Does not account for multitude of accomodations in a real environment NHANES example Find low correlations between performance on some tasks in the Exam Center and responses to question items in the interview For functioning questions For participation questions

14. 11/19/2014 The Social Security Administration’s Disability Decision Process 1980s and 1990s: considerable growth in population receiving disability benefits, with significant changes in the characteristics of beneficiaries (younger, mental impairments) and introduction of the return to work program. SSA interested in improving the decision making process as well as determining the true number of people eligible for benefits under the current system.

15. 11/19/2014 The Social Security Administration’s Disability Decision Process Designed and piloted a population survey Identified people with functional limitations Invited those identified to take part in a physical exam Had the results of the exam evaluated by program adjudicators Pilot survey was extremely expensive and had very low response rates

16. 11/19/2014 The Social Security Administration’s Disability Decision Process Requested a review by IOM in 1996 Of the statistical design and content of National Study of Health and Activity Of the decision-making process Committee recommendations: Research needed on how the current processes works the measurement of job requirements role of vocational factors Conduct periodic indepth surveys to measure work disability