Percentage Of Irish Catholics In Weekly Mass: 90% In 1984, 18% In 2011

We spotted this stat today, via MarginalRevolution, that made us think "There has to be a good explanation for that" -

"According to Archbishop Diarmuid Martin of Dublin, in 1984, nearly 90 percent of Irish Catholics went to weekly Mass. In 2011, only 18 percent did." Source

This statistic might have important implications to the Irish people in the medium-term. Such a significant drop in percentage - from 90% to 18% just in 27 years - is huge, and the 18% number looks 'decisive' at first glance. Maybe there is a much deeper change happening here - that kind of drop in any statistic will raise eyebrows for sure. It is to be noted that in 1946, Pope Paul VI called Ireland “the most Catholic country"