Catholic Church in Ireland
In the 2016 Irish census 78.3% of the population identified as Catholic in Ireland; numbering approximately 3.7 million people. Unlike Catholics in the United States, Ireland has seen a significant decline from the 84.2% who identified as Catholic in the 2011 census.
Demography of Northern Ireland
Although there is a strong correlation between religion and national identity, Catholics tending to identify as Irish and Protestants tending to identify as British, this is not an absolute relationship, and the correlation is much weaker amongst Catholics than it is amongst Protestants. Amongst Catholics, geography also plays an important role, with Catholics in heavily Protestant parts of Northern Ireland being more likely to call themselves British and less likely to call themselves Irish than Catholics in more Catholic areas of Northern Ireland. (The reverse is true for Protestants, but to a lesser extent.) In the 2011 census there were four of the twenty-six districts of Northern Ireland, all on the east coast, where more Catholics considered themselves British than considered themselves Irish.