2017 29.2320547945205
2016 29.3601092896175
2015 29.2786301369863
2014 28.9717808219178
2013 29.1145205479452
2012 29.1166666666667
2011 29.4164383561644
2010 30.0320547945205
2009 29.0756164383562
2008 28.9437158469945
2007 29.2602787456446
2006 29.7608219178082
2005 30.0649315068493
2004 29.3379781420765
2003 29.8347945205479
2002 29.3517808219178
2001 29.5076712328767