Reference materials

These materials are designed to help users make the most of census data.

Census 2021 questionnaires

Sample copies of the Census 2021 questionnaires are available to download.

Census 2021 frequently asked questions

A selection of the most frequently asked questions to help you find out more about Census 2021. Last updated on 30 November 2023.

Census 2021 table lookups

Use the Census 2021 table lookups to search all Census 2021 tables by topic. This document will be updated as more data are released. Last updated on 22 June 2023.

Census 2021 statement about data quality

The Census 2021 statement about data quality aims to assist users by providing information on two aspects of quality: the response rate and the item response rate.

Census 2021 guidance note on use of religion question outputs

Census 2021 contained two religion questions, the first on ‘current religion’ and a follow-up question on ‘religion of upbringing’. This guidance note describes the background to the inclusion of religion questions in the census, the processing of census religion data, and the subsequent reporting of census religion results.

Census 2021 comparability

The 2021-2011 Census in Northern Ireland questionnaire comparability report will help users look at differences in the census questionnaires across the 10-year period, between 2011 and 2021.

Census 2021 outputs definitions

This document provides Census 2021 outputs definitions for terms used in the preparation and publication of statistics from the 2021 Census in Northern Ireland. Last updated on 30 November 2023.

Census 2021 variables index

Information collected through the census questions becomes data, which is output through variables. The Census 2021 variables index details each variable and contains information such as the variable definition and categories. Last updated on 22 June 2023.

Census Quality Survey

The Census Quality Survey (CQS) information paper describes the methodology and findings of the CQS in 2021.  In particular, it outlines the extent to which the responses provided in the CQS, to both the household and individual questions, agreed with those captured in the census.

Census 2021 coverage information paper

The coverage information paper describes the approaches taken to adjust for undercoverage and overcoverage in Census 2021, and the quality assurance undertaken to validate the robustness of the data.

Census 2021 addressing information paper

The addressing information paper details the stages of development and creation of the Census Address Register (CAR), including its maintenance and continued development during the operational phase of Census 2021, and its finalisation during data processing.

Census 2021 student information paper

The student information paper outlines the initiatives undertaken in Census 2021, both in the enumeration and data processing phases, to ensure that students were counted accurately.

Census 2021 methodology overview

The purpose of the Census 2021 methodology overview is to provide background information on the process that underpins Census 2021 outputs. Through detailing these processes, users will gain an understanding of the underlying quality of the Census 2021 outputs.

Census 2021 population and household estimates for Northern Ireland - quality assurance report

The purpose of the Census 2021 population and household estimates for Northern Ireland - quality assurance report is to provide an overview of the quality assurance work that has been undertaken by NISRA, in order to ensure that the Northern Ireland census population estimates are of high quality, fit for purpose, and meet the needs of users.

Census 2021 operational report

On 31 January 2022, NISRA published the Census 2021 operational report. This document is a factual account of how the census was conducted and sets out a record of key elements associated with the operational delivery.

Census 2021 data processing overview

NISRA has published an overview of the data processing methods for the 2021 Census. This document outlines the main stages of data processing for Census 2021.