2017 22.7561643835616
2016 22.8975409836066
2015 22.9402739726027
2014 22.8315068493151
2013 22.7772602739726
2012 22.8584699453552
2011 22.6980821917808
2010 23.1950684931507
2009 22.6838356164384
2008 22.3508196721311
2007 22.7860273972603
2006 22.881095890411
2005 23.0479452054795
2004 22.6898907103825
2003 22.827397260274
2002 22.6974285714286
2001 22.3206349206349