2017 29.9060273972603
2016 30.0502732240437
2015 30.0884931506849
2014 29.7679452054795
2013 29.7147945205479
2012 29.7609289617486
2011 29.561095890411
2010 31.0071232876712
2009 30.1408219178082
2008 30.055737704918
2007 30.5558904109589
2006 30.2279005524862
2005 30.5372602739726
2004 30.0662087912088
2003 30.612602739726
2002 29.9659340659341
2001 30.3597260273973