2017 27.4848901098901
2016 27.6114754098361
2015 27.3183561643836
2014 26.9961643835616
2013 27.2202739726027
2012 27.2325136612022
2011 27.2238356164384
2010 27.8213698630137
2009 27.2056338028169
2008 26.8598360655738
2007 27.1986187845304
2006 27.4070945945946
2005 27.2965648854962
2004 27.1268085106383
2003 27.5005617977528
2002 27.0971153846154
2001 27.9164705882353