2017 28.6153392330383
2016 29.0172131147541
2015 28.9890410958904
2014 29.4799043062201
2013 28.6282913165266
2012 28.8388732394366
2011 28.8473484848485
2010 29.4852348993289
2009 28.2287323943662
2008 28.9227722772277
2007 28.8565789473684
2006 28.815652173913
2005 29.1171919770774
2004 28.606162464986
2003 29.0916666666667
2002 28.7659701492537
2001 29.0036253776435