The difference is made up of net factor flows, which in reality includes net profit repatriation by multinationals and interest on the foreign component of the national debt. In Ireland's case, GDP is significantly larger than GNP because of the large US multinational presence here.

  GDP% GNP%
1999 10.7 8.5
2000 9.2 9.5
2001 6.2 3.9
2002 6.1 2.7
2003 4.4 5.1
2004 4.5 4.0
2005 5.5 5.3
2006 5.7 6.5
2007 6.0 4.1
2008 -2.2 -1.8
2009 -6.4 -9.1
2010 -1.1 +0.5
2011 +2.2 -1.6
2012 +0.2 +0.0
2013 +1.3 +5.8 
2014 +8.8 +9.2
2015 +25.1 +13.6
2016 +5.0 +11.5
2017 +7.2 +4.4
2018 +8.2 +6.5
Annual figures from CSO.