2017 27.5991780821918
2016 27.7434426229508
2015 27.4432876712329
2014 27.1797260273973
2013 27.3005479452055
2012 27.325956284153
2011 27.3383561643836
2010 27.9219178082192
2009 27.3309589041096
2008 26.9884726224784
2007 27.4815426997245
2006 27.5924924924925
2005 27.5601123595506
2004 27.2223756906077
2003 27.3801652892562
2002 27.1908256880734
2001 27.1950684931507