Four years of relentless austerity in many of the euro zone’s most debt-hobbled countries have forced many of their youngest and sometimes brightest workers to grab the plane, train or boat and emigrate in search of work. For countries with a long history of emigration, such as Ireland, this is depressingly familar — coming just 20 years after the country’s last debt crisis and national belt-tightening in the 1980s crescendoed, with the exit of some 40,ooo a year in 1989/90 from a population of just 3-1/2 million people.