| Year | Value | | 2020 | 0.58835815714458 | | 2019 | 0.55826780664953 | | 2018 | 0.63857458799522 | | 2017 | 0.65344339256193 | | 2016 | 0.62730719897742 | | 2015 | 0.64967672850315 | | 2014 | 0.67669232790122 | | 2013 | 0.69221623206346 | | 2012 | 1.1101118014292 | | 2011 | 1.0620672076129 | | 2010 | 1.1604251350681 | | 2009 | 1.1712457383972 | | 2008 | 1.1962245503227 | | 2007 | 1.1774278155547 | | 2006 | 0.92003017698981 | | 2005 | 1.7765986426786 | | 2004 | 1.6781574923488 | | 2003 | 1.6990424351294 | | 2002 | 2.0640576468367 | | 2001 | 3.1060711804144 | | 2000 | 5.1328768748308 | | 1999 | 5.1056954600156 | | 1998 | 5.0413126233721 | | 1997 | 4.9892269654782 | | 1996 | 5.0456651382662 | | 1995 | 6.3801711656093 | | 1994 | 4.7034101894678 | | 1993 | 4.6364389866028 | | 1992 | 4.5620854204874 |
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