Purpose: To describe the methods used by the Washington Group on Disability Statistics (WG) to develop internationally comparable questions on disability that can be used worldwide.
Method: The WG approach to developing disability measures included careful consideration of the theoretical and conceptual issues associated with disability, translating disability concepts into measurement tools, and mixed-method evaluations of the proposed questions using both cognitive and field interviewing methodologies.
Results: Disability is a complex construct the measurement of which presents considerable challenges for survey methodologists. The Washington Group on Disability Statistics (WG), a UN Statistical Commission sponsored city group, was established to address the methodological and measurement challenges that have characterized disability statistics and to develop questions for use worldwide that will provide comparable, valid and reliable disability statistics. The WG used a variety of methods to meet these objectives and has finalized a short set disability measure for use in censuses worldwide.
Conclusions: The methodologies adopted by the WG have resulted in question sets that greatly improve the international comparability of disability statistics and will advance our understanding of disability worldwide.