2017 26.6435616438356
2016 26.9909836065574
2015 26.5356164383562
2014 26.5232026143791
2013 27.1018987341772
2012 26.2527322404372
2011 26.366301369863
2010 27.0128767123288
2009 26.1046783625731
2008 25.6846994535519
2007 26.4183962264151
2006 26.5678362573099
2005 27.5838356164384
2004 27.6108108108108
2003 NA
2002 26.5984025559105
2001 26.7320547945205