Start with the source definition
Census 2011 C-20 classifies population by type of disability, age and sex under the questions and reporting process used in that census. The table is valuable historical evidence, but its categories are part of the measurement. A later survey, certificate register or service programme may use a different definition and therefore count a different population.
Read the right geography and denominator
The C-20 family includes geographic products such as the million-plus city series. Check whether a table covers the area you need and whether its age, sex and residence categories match your question. A share within people classified with disabilities differs from a prevalence share within the whole eligible population. Keep the denominator explicit before comparing age groups or places.
Inspect the treatment of multiple disabilities and the source categories before adding rows. Do not assume that categories from two different sources form a consistent classification or that a certificate count measures everyone with a disability in the area.
Connect demographic context to access needs
For an accessible service, use the historical profile to frame questions about who may face barriers. Then investigate the actual setting: access to information, physical routes, communication, equipment and assistance. Population counts do not show whether a particular building, website or transport route is usable. Planning around those practical barriers requires current evidence and input from intended users.
Describe what remains unknown
A 2011 count is not a current prevalence estimate, a count of benefit enrolments or a measure of unmet demand. Avoid treating the absence of a published local breakdown as evidence that no need exists. If later evidence is available, compare definitions, coverage and collection methods before drawing a trend. Keep the historical table useful by labelling it clearly and stating which present-day access questions require further research.