2017 22.5605678233438
2016 22.8398907103825
2015 22.4402826855124
2014 22.4265060240964
2013 22.6637168141593
2012 22.6732522796353
2011 22.5965408805031
2010 23.3141447368421
2009 22.7526645768025
2008 22.5871080139373
2007 22.5169014084507
2006 22.7396551724138
2005 23.2257425742574
2004 22.578247734139
2003 22.6281553398058
2002 22.4943573667712
2001 18.0434782608696