You make it sound like the Irish economy was managed brilliantly. It was just less appallingly incompetent than that in the North - which wasn't managed for growth for more of the period but for maintenance of a minority power group.

The other problem for the North is that it's not even a provincial shithole, like the South. I don't think Belfast is integrated into the global city network (which is the world's actual economy, outside of artificial national boundaries) in the way Dublin is. Basically the North's natural place is as part of Dublin's hinterland but it can't accept or move into that role.