Communal counting: The Northern Ireland census

Communal counting: The Northern Ireland census
by Ferre WOUTERS for FactCheckNI
6 March 2019

In Northern Ireland, much data are reduced to communal categories of “Protestant” and “Catholic”, for the purposes of monitoring the delivery of public services and compliance with discrimination legislation. These two religious denominations are also used as proxy for British unionist and Irish nationalist identities. For some, a Protestant-majority population provides assurance of continuation of the Union with Great Britain; for others, a Catholic-majority population means a call for a referendum for a united Ireland. Thus the decennial exercise of the Northern Ireland population census has an added sensitivity and importance.

This article seeks to explain the data collection by the Northern Ireland Statistics Research Agency and some of their methods in calculating “Protestants” and “Catholics”.

Presbyterian, Church of Ireland, Methodist Protestant and Other Christian (including [non-Catholic] Christian-related denominations) Belonged to or were brought up in Protestant, Other Christian or [non-Catholic] Christian-related denominations
1981 45.9%
1991 42.8%
2001 39.5% 45.6% 53.1%
2011 35.8% 41.6% 48.4%

A Protestant minority since 2011?

The year 2011 “was the first time the Protestant population was not the majority in the history of the region”, according to the fifth Northern Ireland Peace Monitoring Report, published in October 2018. This statement has also been quoted in a recent UNESCO report called Northern Ireland Returning to Violence.

The third Peace Monitoring Report from 2014 examined data from the 2011 census in Northern Ireland and found that “the headline result was the narrowing of the gap between Catholics (45.1 per cent) and Protestants (48.4 per cent)”. The 45%/48% figure has been widely shared by media outlets: BBC, Belfast Telegraph [1] [2], Irish Times, iNews.

The press release for the 2011 Census explained that “the prevalence rates for the main religions were: Catholic (41 per cent); Presbyterian (19 per cent); Church of Ireland (14 per cent); Methodist (3.0 per cent)”. However, right underneath, it also said that “bringing together the information on Religion and Religion Brought up in, 45 per cent of the population were either Catholic or brought up as Catholic, while 48 per cent belonged to or were brought up in Protestant, Other Christian or Christian-related denominations”.

What does this “information on Religion and Religion Brought up in” contain, and was 2011 really the first time the majority of the population of Northern Ireland was not Protestant?

Belonging to a religion in Northern Ireland

Every ten years a census survey is held in Northern Ireland. Among the questions posed is one asking to “what religion, religious denomination or body” you belong. The answers to this question are variables that “classify a person by the Religion they consider themselves to belong to, or if the person does not belong to a religion, they could select ‘no religion’”.

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Three of the given answers to this question are Protestant churches: “Presbyterian Church in Ireland”, “Church of Ireland”, and “Methodist Church in Ireland”. Together they represented 35.8% (19.03%, 13.74%, and 3% respectively) of the population in 2011.

The three main Protestant churches have represented less than 50% of the population since 1981, when 45.9% of the population responded that it belonged to one of these three Christian denominations. (The 1981 Census, however, was conducted in difficult circumstances, and a campaign of non-cooperation was held in some areas which, according to NISRA, “resulted in a lower than expected figure for those stating ‘Catholic’ and a higher than expected figure for ‘Not stated’”). Ten years later, the percentage of these three Christian denominations declined to 42.8%.

Belonging to a religion in Great Britain and Ireland

In its proposal document for the 2011 Census, NISRA notes that “the formats of the religion questions proposed in the rest of the UK are different, reflecting local requirements and populations”, but “they are sufficiently comparable for the purposes of providing broad UK statistics”.

The religion question in Scotland provides three options for the Christian religion: “Church of Scotland”, “Roman Catholic”, and “Other Christian”. In England and Wales, there is one category: “Christians (including Church of England, Catholic, Protestant and all other Christian denominations)”. The given answers in Ireland contained four Christian options: “Roman Catholic”, “Church of Ireland”, “Presbyterian”, and “Orthodox”. People could also write down other Christian-related denominations.

Table: All respondents, religion belonging, by country, 2011 Census:

Christian Muslim Other No Religion Not Stated
Northern Ireland 82.3% 0.2% 0.6% 10.1% 6.8%
Scotland 53.8% 1.4% 1.1% 36.7% 7%
England & Wales 59.3% 4.8% 3.6% 25.1% 7.2%
Ireland 90.5% 1.1% 0.9% 5.9% 1.6%

Table: Respondents belonging to Christian religion, denomination by country, 2011 Census:

Roman Catholic Presbyterian (Ireland) Church of Scotland Church of Ireland Other Christian
Northern Ireland 40.8% 19.1% 13.7% 8.8%
Scotland 15.9% 32.4% 5.5%
Ireland 84.2% 0.5% 2.8% 3%

(Figures for England & Wales are not applicable; religion denomination not asked.)

Catholics, Protestants, and others in Northern Ireland

To compare figures for Catholics and Protestants, all Protestant denominations have to be included to obtain a single category of Protestants. As seen above, the survey leaves open the option to write in your religion, if you belong to another denomination than the given answers. A full list of all religions answered to the 2011 religion question can be founded here.

Since 2001, the analysis of the religion question codes all responses into four categories:

  1. “Catholic”
  2. “Protestant and other Christian”
  3. “Other religions and philosophies”
  4. “No religion or not stated”


Catholic” (1) adds up “Roman Catholic” with the written answers “Catholic Apostolic Church”, “Ukrainian Catholic”, “Greek Catholic”, and “Catholic”.

Other Christian/Other religions

Other responses were categorised as “Other Christian (including Christian-related)” (2) or “Other Religions and Philosophies” (3), which was done “on the basis of the best available information”. The former category includes Protestant religions such as “Pentecostal” and “Free Presbyterian”, as well as other Christian religions as “Church of England” or “Jehovah’s Witness”. The most indicated other religions were “Baptist” (1% of total population) and “Christian” (0.8%) (see Religion – Full Detail: QS218NI). NISRA acknowledges “that the categorisation of some of the smaller religions is open to interpretation”.

All other stated religions, such as “Muslim” or “Hindu”, were included into the category “Other Religions and Philosophies” (3).

Before 2001, the “Protestant and Other Christian” category did not exist. Religions, apart from the four main churches, were not broken up into two separate groups (“Other Christian” and “Other religions”), but were instead brought together into the group “Other denominations”. However, this latter group later got added with the three main Protestant churches, to provide comparisons over years.

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The percentage of “Protestant and other Christian” went down from 45.6% in 2001 to 41.6% in 2011. Meanwhile, the percentage of “Catholics” remained stable. NISRA notes “this can be partly explained by an increase in the proportion of people who either had no religion or no stated religion (from 14 per cent to 17 per cent) and the more than doubling of the prevalence rate for Other religions (from 0.3 per cent to 0.8 per cent)”.

No religion or not stated

Those who indicated they were “Atheist”, “Jedi Knight”, and others were included in the “No religion or not stated” (4) category, along with people who gave no response to the question.

Catholics, Protestants, and others in Great Britain and Ireland

In Scotland, the category “Other Christian” is also shown in the census results. However, there was no coding of write-in answers. These answers “were coded to ‘Other Christian’ and ‘Another religion’ solely on the basis of which box was used”, since two separate write-in boxes for “Other Christian” and “Another religion” were provided. Furthermore, the category was not taken together with “Church of Scotland” into one category of “Protestant and other Christian”.

In a report by Central Statistics Office, which compares the 2011 census results of Ireland and Northern Ireland, the category “Protestant and Other Christian” was also created for Ireland; 6.3% of the Irish population belonged to that category.

For the England and Wales census, there are no subcategories of the “Christian” response option.

Religion brought up in, in Northern Ireland

A 1999 White Paper brought up an additional question about religion to be included in the 2001 census: “A question on religion has traditionally been included in the census in Northern Ireland, where the information is used to help in the monitoring of policies on equality issues. The question will be similar to that asked in the 1991 Census, but in addition, respondents who indicate ‘no religion’ will be asked to record the religion in which they were brought up (if any)”.

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In the methodology document of the 2001 census, it is stated that “the resultant community background data are of use in informing employment and other equality monitoring”.

The new question is only meant for those who stated they belonged to no religion and those who did not answer the “belonging to” question. Responses to the additional question are coded into the same four categories as ascribed above.

The Census Act (Northern Ireland) 1969 indicates that those who do not complete the question about religion “shall not be subject to any penalty for refusing to do so”. Accordingly, and unlike other questions, the percentage of the population who did not state a religion is given in the results. Normally, missing responses are imputed using standard statistical procedures.

In the UK, the Canadian Census Edit and Imputation System is used for imputation. It is a system developed by Statistics Canada, based on the “Nearest-neighbour Imputation Methodology”. It identifies a set of “nearest neighbours” as similar as possible to each non-respondent, not just for individuals, but for an entire household. These nearest neighbours serve as donors for missing answers.

Imputation is applied to the additional question (“religion brought up in”), meaning the percentage of non-respondents disappears in the adjusted results. 44% of those who self-categorised as “No religion or not stated”, or 7.5% of the whole population, did not give a response to this question. But by using the same statistical imputation as with other questions, 55,345 non-respondents were added to “Catholic” and 59,835 to “Protestant and other Christian” as their religion being brought up in.

The answers to the additional question are then included into the main religion question. This means the four coded categories got adjusted into:

  1. “Belonging to or brought up as Catholic”
  2. “Belonging to or brought up in Protestant or other Christian denominations”
  3. “Belonging to or brought up in other religions or philosophies”
  4. “Belonging to or brought up in no religion”

In the 2011 Census, 123,162 persons who responded to the original religion belonging question with “No religion or not stated” were added to the new “Belonging to or brought up in Protestant and Other Christian denominations (including Christian related)” category, and 79,352 such persons to the “Belonging to or brought up Catholic” category. People “belonging to or brought up in no religion”, are those who answered “None” to both the main and the additional question.

The table below summarises the changes resulting from the additional question:

Religion Religion brought up in (No religion or not stated) Religion or religion brought up in
Protestant and other Christian 41.6% +6.8% 48.4%
Catholic 40.8% +4.4% 45.1%
Other religions and philosophies 0.8% +0.1% 0.9%
No religion 10.1% -4.5% 5.6%
Not stated 6.8% -6.8%

At 48.4%, it is true that 2011 was the first time that this category of “Belonging to or brought up in Protestant and Other Christian denominations” represented less than half of the Northern Ireland population.

Religion brought up in, in Great Britain and Ireland

The question asking for the religious background of non-respondents and non-religious people is specific for Northern Ireland. A similar additional question is not asked in England and Wales, nor in Ireland.

In Scotland, the “brought up in” question was asked in the 2001 census, in addition to a “belonging to” question. It differed from the Northern Ireland census in that the “brought up in” question had to be answered by everyone (i.e. not exclusively by non-respondents or non-religious people). Consequently, the responses were coded independently of the “belonging to” question. 9.7% of people who in 2001 belonged to a Christian religion did not state the same religion for where they were brought up in. Likewise, 41.6% of people who stated they belonged to no religion stated a different response to what they were brought up in. In 2011, the “brought up in” question was dropped from the Scotland Census, due to “limited user demand”.


The percentage of the population that is considered “Protestant” depends on the definition being used. Seen as belonging to any of the three main Protestant churches, less than 50% of the population has been Protestant since 1981. Adding people who belong to other Christian-related denominations, there has been a Protestant minority since 2001. Including non-religious people and non-respondents who were brought up in Protestant or other Christian denominations, less than half of the population has been Protestant since 2011.

In addition to a religion belonging question, Northern Ireland is unique in the British Isles for asking a further religious background question. For those who answered the census question as belonging to no religion, or did not answer that question at all, “religion brought up in” is imputed using a nearest neighbour method. This produces data that other statutory agencies find useful.

In any case, the adjusted combined figures (6.5%) of those who responded “No religion” (5.6%) and “Other religion and philosophies” (0.9%) is greater than the spread between the adjusted figures of “Protestant” (48.4%) and “Catholics” (45.1%). Protestants are just one of several minorities in Northern Ireland.

Cover image showing relative populations between Protestants (red) and Catholics (blue); source: Northern Ireland Peace Monitoring Report, Number Five, October 2018.