Bugger all. Most migration is out of Ireland as a whole - with punters going to the UK, America, Canada and Australia (in order of preferance!). I knew studying geography at uni would one day come in useful......
There always used to be plenty of cross-border migration - mainly cattle (depending on subsidies in UK or Eire) - or 'visitors' coming North for a short while, trying to murder someone, and running away.
Back to demographics, isn't it the case that, the safer and more economically secure people feel, the less big the families? Could be Gerry and the boys have done themselves out of business
Hopefully if the nationalist element of the population is becoming more prosperous, middle class and having less children then they will be less likely to vote for Sinn Fein and more likely to vote for the SDLP which engages in normal politics and doesn't have its own illegal private army champing at the bit to start its 'war' once again.
PTP - you are right, if it annoys Gerry then its fine with me! He really needs taking down a peg or too (in a strictly non-violent sense of course, I wouldn't want to be misinterpreted...)