2017 28.2697222222222
2016 27.8445355191257
2015 28.0364383561644
2014 28.0608219178082
2013 28.173698630137
2012 28.8142076502732
2011 28.5775342465753
2010 29.321095890411
2009 28.5783561643836
2008 28.3893442622951
2007 28.6206896551724
2006 28.2036211699164
2005 28.4463687150838
2004 27.8827868852459
2003 28.205604719764
2002 27.8869706840391
2001 28.2634560906516