2017 23.5356466876972
2016 NA
2015 22.0064516129032
2014 23.2162857142857
2013 22.9427027027027
2012 21.7645161290323
2011 23.3857534246575
2010 23.9509589041096
2009 23.4687671232877
2008 23.3170149253731
2007 23.8593220338983
2006 23.4525679758308
2005 23.5051428571429
2004 23.2780864197531
2003 23.1260869565217
2002 23.4737003058104
2001 23.2673295454545