| Year | Value | | 2020 | 0.88892126736976 | | 2019 | 0.87614318394295 | | 2018 | 0.88399596335654 | | 2017 | 0.88646379167504 | | 2016 | 0.9135102829208 | | 2015 | 0.92433683713692 | | 2014 | 0.93323595110594 | | 2013 | 0.94121688915005 | | 2012 | 0.95353068893012 | | 2011 | 0.94981434088034 | | 2010 | 0.99359844966812 | | 2009 | 0.98007047351528 | | 2008 | 1.0706713037502 | | 2007 | 1.0810395377223 | | 2006 | 1.1073610303796 | | 2005 | 1.1751548700889 | | 2004 | 1.1773960504681 | | 2003 | 1.2560483876958 | | 2002 | 1.3225549459636 | | 2001 | 1.3483750255159 | | 2000 | 1.4357752376841 | | 1999 | 1.555764692382 | | 1998 | 1.6391782609178 | | 1997 | 1.6885581401168 | | 1996 | 1.7824688737121 | | 1995 | 1.8309160835138 | | 1994 | 1.5531916949706 | | 1993 | 1.5572459182339 | | 1992 | 1.635558304754 | | 1991 | 1.7314343113286 |
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