2017 29.0720547945205
2016 29.4128415300546
2015 29.1191780821918
2014 28.8764383561644
2013 28.9753424657534
2012 29.1207650273224
2011 29.3243835616438
2010 30.0320547945205
2009 28.5731506849315
2008 28.4270491803279
2007 28.8024657534247
2006 28.886301369863
2005 29.2956164383562
2004 28.6196721311475
2003 27.8818181818182
2002 NA
2001 NA