Does FF benefit from fault-line in voting system?

HOW does it come about that Fianna Fáil, with 42% of the vote, secures 78 seats in Dáil Éireann when 42% ought, strictly speaking, to yield only 68-70 seats?

Is there a fault-line in our much admired system of proportional representation? This outcome may not be as disproportionate as Tony Blair’s majority in the British parliament on 36% of the vote, but nevertheless it is the difference between government and opposition.

Dr Gerald Morgan