2017 26.766301369863
2016 26.8918674698795
2015 NA
2014 NA
2013 26.159022556391
2012 26.9952991452991
2011 26.2161654135338
2010 26.8611111111111
2009 26.1585227272727
2008 25.8398648648649
2007 26.0079439252336
2006 26.1932352941176
2005 26.6486111111111
2004 25.8991803278689
2003 26.0063186813187
2002 26.0600694444444
2001 NA