Why are DDI’s databases focused on functional difficulties?
Date: Dec. 17th 2025
Overview
The Disability Data Initiative (DDI) has been analyzing quantitative disability data from household surveys and population and housing censuses in order to produce disability-disaggregated data (or statistics). Identifying persons with disabilities in such datasets is challenging and there is no gold standard on how to do that. We have been identifying persons with disabilities through brief sets of question on functional difficulties. Why such a focus on functional difficulties?
What Are Functional Difficulties?
Functional difficulties are difficulties that an individual may experience with particular bodily functions such as seeing, or basic activities such as walking or feeding oneself. In 2017, the United Nations adopted guidelines for collecting disability data in national censuses recommending that four domains be considered essential to determine disability status in a census to facilitate international comparisons: (i) walking, (ii) seeing, (iii) hearing, and (iv) cognition. In addition, the guidelines note that two other domains have also been identified for inclusion in censuses: self-care and communication.
Washington Group Short Set (WG-SS)
The Washington Group (WG) Short Set (WG-SS) of questions meets these guidelines and is the result of an international effort to produce internationally comparable data. The WG-SS is a set of six questions developed by the Washington Group on Disability Statistics (WG). The WG-SS starts with an optional introduction as follows: “The next questions ask about difficulties you may have doing certain activities because of a health problem.” It has six questions: (1) “Do you have difficulty seeing, even if wearing glasses?” (2) “Do you have difficulty hearing, even if using a hearing aid?” (3) “Do you have difficulty walking or climbing steps?” (4) “Do you have difficulty remembering or concentrating?” (5) “Do you have difficulty with self-care (such as washing all over or dressing)?” (6) “Do you have difficulty communicating?” For each question, the answers are as follows: no difficulty, some difficulties, a lot of difficulties, or cannot do at all.
Other Functional Difficulty Questions
Some countries have been using other functional difficulty questions that follow the 2017 UN guidelines but do not exactly use the questions or answers of the WG-SS. The DDI has also been documenting the availability of other functional difficulty questions. In its analyses of microdata, the DDI has prioritized datasets with the WG-SS for international comparability but for some countries it has used data with other functional difficulty questions.
Why a Focus on Data from Functional Difficulty Questions?
The DDI has prioritized using surveys and censuses with functional difficulty questions, as they are understandable in a variety of contexts and considered internationally comparable. The term ‘disability’ as such is not included in functional difficulty questions as individuals and communities may have different understandings of the term and in some contexts, there could be stigma associated with the term.
Such functional difficulty questions, the WG-SS in particular, have recently been included in a growing number of national population and housing censuses and household surveys as shown in the DDI’s Disability Statistics – Questionnaire Review (DS-QR) Database.
With surveys and censuses that have such questions, the DDI has produced disability-disaggregated statistics for adults in countries around the world. They are available in the Disability Statistics – Estimates (DS-E) Database. That way, we are figuring out if persons with disabilities are at risk of having their rights not realized in terms of education, employment, health and poverty in various country contexts.
Suggested citation: Disability Data Initiative (DDI). (2025). Why are DDI’s databases focused on functional difficulties? Dec. 17th 2025. Accessed at https://www.disabilitydatainitiative.org/publications/DDIblog2025-03