2017 23.1711711711712
2016 23.4232240437158
2015 23.184375
2014 23.2494845360825
2013 23.8653846153846
2012 23.1417647058824
2011 23.1572602739726
2010 23.7139204545455
2009 23.0629737609329
2008 22.751497005988
2007 23.124064171123
2006 22.5822085889571
2005 23.5365650969529
2004 23.645652173913
2003 NA
2002 23.219801980198
2001 23.0494413407821