2017 30.7197260273973
2016 30.9562841530055
2015 30.7687671232877
2014 30.44
2013 30.6797260273973
2012 30.6060109289617
2011 30.6975342465753
2010 31.3205479452055
2009 30.4054794520548
2008 30.1073770491803
2007 30.5054794520548
2006 30.5846575342466
2005 30.7720547945205
2004 30.2172131147541
2003 30.5279452054795
2002 30.1583561643836
2001 30.2994520547945