2017 NA
2016 4.53152173913043
2015 3.67506849315068
2014 3.9772602739726
2013 6.52493150684931
2012 5.44289617486339
2011 6.9641095890411
2010 6.48958904109589
2009 4.67698630136986
2008 4.65765027322404
2007 4.97506849315069
2006 4.42630136986301
2005 6.07479452054794
2004 6.21448087431694
2003 4.02931506849315
2002 4.58849315068493
2001 4.05780821917808