2017 21.861095890411
2016 21.6754098360656
2015 21.6501369863014
2014 21.3435616438356
2013 21.4194520547945
2012 21.6131147540984
2011 21.4191780821918
2010 21.7
2009 21.1865753424658
2008 20.896174863388
2007 21.0775342465753
2006 21.7252054794521
2005 21.7043835616438
2004 21.6051912568306
2003 21.3476712328767
2002 21.7158904109589
2001 21.4797260273973