2017 24.0142465753425 2016 24.0811475409836 2015 23.5043835616438 2014 22.5580821917808 2013 22.7383561643836 2012 23.0144808743169 2011 24.0698630136986 2010 24.5969863013699 2009 23.7241095890411 2008 23.4773224043716 2007 23.8331506849315 2006 23.7151098901099 2005 23.8969863013699 2004 24.128813559322 2003 NA 2002 NA 2001 NA