2017 22.9972602739726
2016 23.1549180327869
2015 23.0884931506849
2014 22.8260273972603
2013 22.7561643835616
2012 22.9874285714286
2011 22.7767123287671
2010 23.4386018237082
2009 22.9109792284866
2008 22.8396774193548
2007 23.4032110091743
2006 23.6092485549133
2005 23.7737142857143
2004 23.2130681818182
2003 23.5554572271386
2002 23.4137426900585
2001 23.258064516129