2017 23.7172602739726
2016 23.9792349726776
2015 23.8986301369863
2014 23.7627397260274
2013 23.7120547945205
2012 23.8374316939891
2011 23.6967123287671
2010 24.2298630136986
2009 23.4778082191781
2008 23.170218579235
2007 23.5238356164384
2006 23.5523287671233
2005 23.6709589041096
2004 23.3071038251366
2003 22.2727272727273
2002 NA
2001 NA