2017 29.8994520547945
2016 30.3385245901639
2015 29.5980821917808
2014 29.413698630137
2013 29.3835616438356
2012 29.3754098360656
2011 29.6408219178082
2010 30.3498630136986
2009 29.6380821917808
2008 29.4704918032787
2007 30.1490410958904
2006 29.98
2005 29.6167123287671
2004 28.9513661202186
2003 29.1624657534247
2002 28.9895890410959
2001 28.9142465753425