Model Disability Survey

The Model Disability Survey is a general-population survey developed jointly by the World Health Organization and the World Bank to generate comprehensive, internationally comparable data on functioning and disability. Unlike instruments that classify people as disabled or not, it operationalizes the biopsychosocial model of the WHO ICF, treating disability as the outcome of an interaction between a person's intrinsic capacity and the environment in which they live. The survey collects detailed self-reported information on how much difficulty people have across many domains of functioning, distinguishing what a person can do in a standardized environment (capacity) from what they actually do in their own environment (performance), and it separately measures environmental barriers and facilitators. As documented by Sabariego and colleagues in 2022, these responses are combined using a Rasch measurement model into a single metric scale, so that disability is represented as a continuum running across the whole population rather than as a yes/no category. The result is a graded picture of functioning suited to prevalence estimation, equity analysis, and policy on a comparable metric.