2017 21.5197260273973
2016 21.6027322404372
2015 21.2230136986301
2014 21.0019178082192
2013 21.1306849315068
2012 21.1844262295082
2011 21.2246575342466
2010 21.6608219178082
2009 21.0539726027397
2008 20.7401639344262
2007 20.9053731343284
2006 21.1454794520548
2005 21.4479452054795
2004 20.9866120218579
2003 21.0865753424658
2002 20.733698630137
2001 20.6306849315068