The remarkable success of this tax haven means that roughly 20 percent of Irish gross domestic product (G.D.P.) is actually “profit transfers” that raise little tax for Ireland and are owned by foreign companies. Since most of these profits are subject to the tax code, they are accounted for in Ireland where they are lightly taxed; they should not be counted as part of Ireland’s potential tax base. A more robust cross-country comparison would be to examine Ireland’s financial condition ignoring these transfers. This is easy to do: a nation’s gross national product excludes the profits of foreign residents. For most nations, gross national product and G.D.P. are near-identical, but in Ireland they are not.
When we adjust Ireland’s figures accordingly, the situation is dire. The budget deficit was about 17.9 percent of G.N.P. in 2009, and based on European Commission projections (and assuming the G.N.P.-G.D.P. gap remains the same) it will be roughly 14.6 percent in 2010 and 15.1 percent in 2011, while the debt-to-G.N.P. ratio at the end of this year is expected – by our calculation – to be 97 percent, and 109 percent at the end of 2011. These numbers make Ireland look similarly troubled to Greece, with a much higher budget deficit but lower levels of public debt.
That's Simon Johnson, here is more.