2017 30.0605479452055
2016 30.1469945355191
2015 30.186301369863
2014 29.9860273972603
2013 30.1383561643836
2012 29.7391304347826
2011 29.8838356164384
2010 30.3208219178082
2009 29.806301369863
2008 29.6213114754098
2007 29.9509589041096
2006 30.033698630137
2005 30.0841095890411
2004 29.5909836065574
2003 30.0320547945205
2002 30.1419178082192
2001 29.8331506849315