2017 NA
2016 NA
2015 NA
2014 NA
2013 NA
2012 NA
2011 NA
2010 NA
2009 NA
2008 27.0434426229508
2007 27.9657534246575
2006 28.2887671232877
2005 28.0172602739726
2004 27.2860655737705
2003 28.2032876712329
2002 27.8912328767123
2001 28.6011049723757