2017 29.2452054794521
2016 29.3609289617486
2015 29.3060273972603
2014 29.0301369863014
2013 29.2120547945205
2012 29.1934426229508
2011 29.2690410958904
2010 29.8841095890411
2009 29.0838356164384
2008 28.8013661202186
2007 29.3427397260274
2006 29.4884931506849
2005 29.7660273972603
2004 29.0489071038251
2003 29.4482191780822
2002 28.9575342465753
2001 29.2912328767123