2017 26.8654794520548
2016 26.8232835820896
2015 26.6235616438356
2014 26.3013698630137
2013 26.4969863013699
2012 26.4838797814208
2011 26.5893150684931
2010 27.1991780821918
2009 26.2958904109589
2008 26.146174863388
2007 26.3519163763066
2006 26.8005479452055
2005 26.9373961218837
2004 26.2061162079511
2003 27.1445652173913
2002 25.2709677419355
2001 26.6090659340659