From 1821 until 2011, the male and female populations of the 26 counties of the modern-day Republic of Ireland grew at a relatively similar rate, however some fluctuations did occur. During this time, the entire island of Ireland was a part of the United Kingdom of Great Britain and Ireland, after both islands were united by the Acts of Union in 1800. This graph shows the populations of the 26 counties that would later form the Republic of Ireland in 1921, and does not include the six counties that became known as Northern Ireland.

As we can see, both populations follow a relatively similar trend throughout their respective histories. In the first three entries, women outnumber men by 70,000 to 120,000, although these figures do not include military personnel which would narrow this margin. Both populations fall at a similar rate during and after the famine, however the male population does fall slightly faster, possibly due to an increased rate of emigration among males. Another point where both populations differ is in the early twentieth century, where the female population declines in a relatively smooth curve, although the male populations peak in the census data before and after both world wars. From 1956 onwards both populations follow a very similar trend, and grow at the same rate. The difference in population sizes never exceeds 30,000 people, until the final entry in 2011 where the population of men is 2.27 million and the population of women is 2.31 million.

This data collection contains data primarily from both the 1841 and 1851 Census of Ireland used in Fernihough and Ó Gráda (2022). Also contained, where available, are population counts from the 1821 and 1831 censuses. The data collection also includes an amended version of the Civil Parish Shapefile from townlands.ie (OpenStreetMap Ireland, 2020). Both data sources were adjusted to ensure concordance. The towlands.ie data is open data is open data, licensed under the Open Data Commons Open Database License (ODbL). Please contact Alan Fernihough for further details or queries. The “shapefile” files are the GIS files one needs to load the spatial boundaries. The census data is included in the “data.csv” file and one must merge this to the shapefiles to work with these data. However, this is a simple process. The file “load and join.R” is an example of how this could be performed using the R statistical software package.

The island of Ireland is split into 32 different counties, and from 1800 until 1921 the whole island was a part of the United Kingdome of Great Britain and Ireland (although Britain had been a controlling presence on the island for considerably longer than this). In 1921 the island was split into two separate states, where the six counties with the highest population of Protestants formed part of the United Kingdom of Great Britain and Northern Ireland, and the other 26 counties became the Independent Republic of Ireland. From 1821 until 1841, the population of these 26 counties was growing steadily, until the Great Famine from 1845 to 1849 swept across the island, particularly devastating the west and south.

The famine was caused by a Europe-wide potato blight that contributed to mass starvation and death throughout the continent, although it's impact on Ireland was much harsher than anywhere else. The potato blight affected Ireland so severely as the majority of potatoes in Ireland were of a single variety which allowed the disease to spread much faster than in other countries. People in the west and south of Ireland were particularly dependent on potatoes, and these areas were affected more heavily than the north and west, where flax and cereals were the staple. As the potato blight spread, the population became increasingly reliant on dairy and grain products, however a lot of these resources were relocated by the British military to combat food shortages in Britain. Due to disproportional dependency on potatoes, and mismanagement by the British government, over one million people died and a further one million emigrated. The Great Famine lasted from just 1845 to 1849, but it's legacy caused almost a century of population decline, and to this day, the population of Ireland has never exceeded it's pre-famine levels.

The population decline continued well into the twentieth century, during which time the Republic of Ireland achieved independence from the British Empire. After centuries of fighting and rebellion against British rule, Irish nationalists finally gained some independence from Britain in 1921, establishing an Irish Republic in the 26 counties. There was a lot of conflict in Ireland in the early 1900s, through the War of Independence and Irish Civil War, however the population of the Republic began growing again from the 1960s onwards as the quality of life improved and the emigration rate declined. The population was at it's lowest from 1926 to 1971, where it remained at just under three million, but in the following fifty years the population has grown by over two million people.

The purpose of the project was to provide machine-readable economic and social history statistics relating to the whole of Ireland for the period 1821-1971. Further information about the project is available on the QUB Centre for Data Digitisation and Analysis website.