2017 28.0591780821918
2016 28.1232240437158
2015 28.0635616438356
2014 27.8731506849315
2013 27.9465753424658
2012 28.1171428571429
2011 28.1145205479452
2010 28.9094224924012
2009 28.0661721068249
2008 28.0806451612903
2007 29.0261467889908
2006 29.5350427350427
2005 29.8345714285714
2004 28.7497159090909
2003 29.2662721893491
2002 28.824269005848
2001 28.6825806451613