A comprehensive measure to determine disability includes all six domains of functioning: seeing, hearing, walking/climbing steps, remembering/concentrating, self-care and communication.
As noted in the 3rd revision of the Principles and Recommendations for Population and Housing Censuses (UNSD: https://unstats.un.org/unsd/statcom/doc15/BG-Censuses.pdf) four domains of functioning: seeing, hearing, walking/climbing steps, and remembering/concentrating are considered the most essential in determining disability status from census data in a way that would allow for international comparison. In circumstances where it is impossible for reasons of time or space to ask all six questions, these four domains should be included as the essential minimum.
Furthermore, it has come to our attention that for reasons related to culture, in certain countries enumerators have had difficulty asking the self-care question. In such circumstances, the omission of this question is permissible.
To illustrate the net effect of asking six versus four questions, data from the 2013 U.S. National Health Interview Survey (NHIS) show that disability prevalence among those 18 years and older (weighted) using all six Short Set questions is: 9.5%. Omitting the questions on self-care and communication reduces the prevalence to: 9.3%. Disability is not a uniquely unidimensional or single domain phenomenon. Among those with functioning difficulties (over six domains) in the 2013 NHIS sample, 27% have multiple difficulties. It could further be demonstrated that 92% of those with self-care difficulties and 78% of those with communication difficulties were included among those identified as having difficulties in the other four domains of functioning (that is, they were not explicitly excluded but omitting the question makes it impossible to estimate the population with this type of functional difficulty and to look at the impact on participation).