Does The WG-SS Identify All People With Disabilities, And Does It Matter?
The answer to the first question posed in this blog is easy. No, the WG-SS does not identify all people with disabilities. First, there is no gold standard to identify all people with disabilities for all purposes. In a previous blog we discussed, for example, the difference between identifying people with disabilities for monitoring the SDGs versus determining eligibility for specific programs.
But even for the purpose that the WG-SS were developed – to identify people at risk of exclusion because of activity limitations – we know the WG-SS does not capture everyone. To identify all people would require many more than six questions. However, we are limited in the number of questions we can ask, especially on a census where space is very tight.
Space is also an issue on surveys. To disaggregate the SDGs we would like to see all household surveys used for SDG indicator production have the WG-SS on them. The more questions we ask to be put on a survey, the less chance that they will be included because of cost and time constraints. So we must consider diminishing returns. How much extra value will be added for the purpose the WG-SS is intended by adding additional questions?
The Washington Group Extended Set of questions was designed to capture those persons at risk for exclusion that might be missed by the WG-SS. In the table below using data from the US, you can see how adding questions from the WG-ES on upper body difficulties and psycho-social difficulties, two domains omitted from the short set, affects prevalence. Adding these domains does increase the number of people identified, but at the cost of additional questions. For example, in the US, the WG-SS yields a 9.5% prevalence rate, which increases only slightly to 10,0% if the two upper body questions are added from the extended set. It is believed, however, that more people with psycho-social disabilities will be missed by the WG-SS. Some are identified through the communication, cognition, or self-care question, but not all. In the US, 3.6% of the population is identified as having a disability based on the anxiety and depression questions, but 2.1% of the population so identified were also identified by at least one of the WG-SS questions.
That means that using only the WG-SS will miss 1.5% of the population that has a psychosocial disability. Of course, only using the WG-SS will mean that the remaining 2.1% of the population that have psychosocial disabilities will not be identified as having that type of disability, but most likely by the cognitive or communication domain.