jjxbr, you refer to migrants here, by that do you mean internal migration? In an earlier post you refer to immigration as a possibility for the bulge but looking at Irish birth rates you'd have expected the outcome you show above.
Throughout the 50's, 60's and 70's there were approx 60,000 births a year. In the late 70's and early 80's this jumped to 75,000 before falling back to around 50,000. These people born in the late 70s, early 80's would now be in the 25-34 age range and as such the big bulge that we are now seeing at that age group is more likely down to the baby boom of late 70's than immigration
The number of births stayed around 48k-52k throughout the early 90s before increasing steadily each year to around 75k last year. There seems to be another, longer lasting, wave coming in the not too distant future. Universities are already looking at funding options in 3-4 years time when they get hit with a large increase in 17 year olds (hence their arguments for reintroducing fees) and schools are gearing up for the current high birth rate.
I can't find data on a county by county breakdown hence my reference to migration above as it's not clear in what counties the mini baby boom of 70s was or it it was nationwide.
I have no idea. More analysis is needed. I would have expected learned institutions like the ESRI to perform this.
All you can tell is that they are migrants. The source - internal or external - can only be inferred by cross-referencing to other data. You can also track population numbers by age/age cohort across censuses to identify when the migration occurred.
If you make me a professor in the ESRI and give me a stick-on beard, I will produce the analysis.
There is mixed information here:
CNA12 Population by County, Year, Sex and Usual Residence One Year Previous - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
CNA32 Population Born Outside County of Enumeration by County and Year - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
CNA19 Population Change Components by County, Year and Statistic - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
CNA31 Population by County, Year and Country of Birth - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
PEA03 Estimated Population Migration by Sex, Age Group, Year and Origin or Destination - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
PEA02 Estimated Population Migration by Sex, Year, Origin or Destination and Country - http://www.cso.ie/px/pxeirestat/Statire ... Language=0
The CSO used to publish population by age cohort and county.