2017 29.0854794520548
2016 28.8120218579235
2015 28.4443835616438
2014 28.2682191780822
2013 28.3934246575342
2012 28.603825136612
2011 28.7890410958904
2010 29.3709589041096
2009 28.673698630137
2008 28.494262295082
2007 28.612602739726
2006 28.8471232876712
2005 29.0120547945205
2004 28.0224043715847
2003 28.3646575342466
2002 28.2143266475645
2001 27.9944444444444