Over the past century two ratios which have been positive, the ratio of Irish in the UK and visa versa and the ratio of Protestants to Catholics in Northern Ireland, are likely to invert. Currently there are more Irish in the UK and more Protestants in Northern Ireland than visa versa.
Irish in the UK and the Flow of People in the Common Travel Area
If Brexit goes ahead then UK citizens freedom of movement (FoM) will be limited to the UK and Ireland. Irish citizens will retain FoM both within the UK/IE block and also in the EU. This makes Irish citizenship more valuable and unsurprisingly there has been a surge in demand for Irish passports.
Over the past century the flow of people has largely been from Ireland to England, particularly in the aftermath of the 2nd World War when the UK had an insatiable demand for people to rebuild Britain and the Irish economy was weak. This trend reversed in the 1990s in the time of the Celtic Tiger, reversed again briefly in the UKs favour after the GFC, but the flow is now from the UK to IE and is close to record levels at around 20k per year, as illustrated in figure 1.
On average 375,900 people born in Ireland were living in the UK from January 2013 to December 2015, compared with 277,200 UK-born occupants in Ireland in 2016.
Other sources put the number of UK citizens living in Ireland at a bit higher (300k).
The UK population in Ireland is only about 75% of the Irish population in the UK, but given the UK population is about 14 times greater than Ireland, as a fraction of the population the number of UK born citizens in Ireland is over ten times that of the Irish in the UK.
Nearly all the Irish in Britain live in England, so the English figures will give a good picture of the total. Looking closely at UK census data it is clear that the Irish population in England is ageing, with the highest numbers being in the 60-70 cohort. This is to be expected as that was major migration of young adults from Ireland to England in the ’40s and ’50s, who now form this cohort. There has also been a very slight increase in males in their 20s and both sexes in their 40s.
The aging profile of the Irish against the general UK population is more evident in Fig. 3 with the fraction of White Irish children and teenagers being much lower than White British while the fraction of middle aged and elderly higher.
It seems very likely therefore through natural decline both via mortality and migration that the Irish population in England is likely to decline. Indeed on current trends there may well be more UK citizens living in Ireland than visa versa within the next few years.
Demographics in Northern Ireland
It is well known that there is a demographic shift in Northern Ireland between the number of Catholics and Protestants. The borders of Northern Ireland were drawn to give a 2/3 majority of Protestants but this majority is evaporating and within a few years the Catholic population will overtake the Protestant one.
Catholics tend to be Nationalist and Protestants Unionist, with a correlation of greater then 90%.
Two recent surveys indicate that the demographic shift is accelerating rather than slowing down.
The Labour force survey religion report (2017) contains a wealth of data including some very interesting post Census 2011 demographic data as well as historical comparisons. The report runs to 83 pages and goes into considerable detail. It can be accessed in full here. There is also a summary on BangorDub site. The survey indicates that whilst Protestants still outnumber Catholics, it is now by a tiny margin. In absolute numbers by only 7,000 in 2017. Fig. 4 shows the religion of working age adults. Catholics clearly outnumber Protestants but neither are a majority.
For the over 60’s there is a clear Protestant majority as shown in Fig. 5.
The other major survey is the Schools Census 2018 again available on the BangorDub site. This survey has more categories including “Other Christian” and “Non Christian.” It shows that there is no slowing of the demographic shift. Indeed among school age children Catholics easily outnumber Protestants and are now 51% of the NI population.
It seems very likely that there will be more UK citizens living in Ireland than visa versa within the next few years.The Irish are extremely relaxed about this, as like Scotland, immigration is seen as a major positive and not a negative like in England. (Though attitudes in England seem to be changing).
The ratio of Irish in the UK to vica versa may change if Brexit is a tremendous economic success and the Irish economy is very weak by comparison. This seems unlikely – indeed the movement of people seems to be accelerating, with Dublin for example being the clear winner in attracting finance jobs from the City of London. There is a danger of overheating in the Irish economy with the growth rate being the highest in the EU for 5 years with that of 2018 running at 6.7%. The UK economy by comparison has been lacklustre, indeed the UK economy is set for worst year since the financial crisis, says the Bank of England.
It seems inevitable that there will be more Catholics than Protestants in Northern Ireland within the next few years, probably by the 2021 census. It will take a further decade however before there is a majority of voting age adults. The survival of Northern Ireland from the late 2020s onwards critically depends on how happy they are to remain the UK. Indeed a no deal Brexit may mean that Northern Ireland leaves the UK within a few years as many neutrals favour remaining in the EU.