Despite its rich heritage of great writers, Ireland has one of the highest illiteracy rates among the world's developed countries. According to a United Nations study of 12 developed countries that was issued this month, Ireland with a population of 3.6 million, has 500,000 adults - or 23 per cent of the adult population - who are functionally illiterate. That means they cannot read a gas bill, a letter or a newspaper and cannot do the simplest arithmetic.