2017 29.5608219178082
2016 29.8565573770492
2015 29.7950684931507
2014 29.7265753424658
2013 29.5953424657534
2012 29.8478142076503
2011 29.8145205479452
2010 30.5024657534247
2009 29.6087671232877
2008 29.4469945355191
2007 29.7471641791045
2006 29.2920547945205
2005 29.9394520547945
2004 29.4273224043716
2003 29.6057534246575
2002 29.2038356164384
2001 29.4