This post, worth reading as well, in WEIT reminded me to check out the latest Iona Institute survey. Like the 2010 Bishops Conference survey, they have no real good news if you're a Catholic leader.
I've plotted up the first table in the survey as well as total adults in Ireland by age group (blue), collated from the 2006 census figures. In red is the number of adults identifying as Catholic and in green is the number of those Catholics that attended mass in the past week.
It clearly shows that the the younger you are in Ireland, the less likely you are to call yourself a Catholic and very much more so the less likely you are to attend mass regularly. Given how fundamental mass is to the Catholic religion, I think this is a good barometer of how committed someone identifying as Catholic is to their religion. It points towards a big decline in religious Catholics even if people still consider themselves cultural Catholics.
If the trends shown extrapolate into the new generations then we might expect a ongoing but not precipitous fall in religious affiliation but I think the key thing is actually the mass going percentage - that really suggests that even if Ireland remains on paper significantly Catholic for the time being, the reality is that they are mostly cultural or plastic Catholics.
This fits with the results of the 2010 survey which found that only half of Irish Catholics believed in Hell and only three-quarters believed in Heaven, while 10% didn't believe in God. It's also reflected in the perception of their church amongst Catholics in the Iona survey:
Again the 55's and older appear to prop up the figures. So how much of the population is that cohort as a percentage?
Looking at the CSO website in the 2006 census, they account for 20% of the total population (or 26% of everyone over 14 years old) while the 15-54 age group is 59% of the total population (or 74% of everyone over 14 years old).
Of course, as it's actually 77% of the over 54's that are Catholic, that means the older religious group corresponds to 20% of the total adult population of Ireland.