Year | Value | 2022 | 18.905549079345 | 2021 | 18.531979294779 | 2020 | 18.291810705005 | 2019 | 18.506216783022 | 2018 | 18.427384061921 | 2017 | 18.288482286576 | 2016 | 18.18599744828 | 2015 | 18.0149378629 | 2014 | 18.032333910326 | 2013 | 18.054395357285 | 2012 | 18.160847980643 | 2011 | 17.937940791169 | 2010 | 17.613102446119 | 2009 | 17.389326940974 | 2008 | 16.999426407296 | 2007 | 16.372887651982 | 2006 | 16.073192741746 | 2005 | 15.754936286013 | 2004 | 15.628140797816 | 2003 | 15.530191994441 | 2002 | 15.816400093907 | 2001 | 16.134291559067 | 2000 | 16.040859733264 | 1999 | 15.948363606671 | 1998 | 15.750168339534 | 1997 | 15.584499674426 | 1996 | 15.407389647043 | 1995 | 15.260963571233 | 1994 | 15.196899016231 | 1993 | 15.19414325899 | 1992 | 15.221793581757 | 1991 | 15.274083545239 |
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