| Year | Value | | 2020 | 0.73672167760491 | | 2019 | 0.7401249695042 | | 2018 | 0.74776764842659 | | 2017 | 0.74601280456807 | | 2016 | 0.75306072052537 | | 2015 | 0.76095399678107 | | 2014 | 0.76326588230209 | | 2013 | 0.76417727765004 | | 2012 | 0.80352751767995 | | 2011 | 0.80592177279097 | | 2010 | 0.81554325196601 | | 2009 | 0.81737110862509 | | 2008 | 0.81025558981528 | | 2007 | 0.81010961154841 | | 2006 | 0.88010358175258 | | 2005 | 0.87872317848942 | | 2004 | 0.86030063402711 | | 2003 | 0.89887262089638 | | 2002 | 0.91499498567735 | | 2001 | 0.92764858124069 | | 2000 | 0.98777629954364 | | 1999 | 1.0009832558985 | | 1998 | 1.0348734429592 | | 1997 | 1.0543853438483 | | 1996 | 1.0916920661534 | | 1995 | 1.1050423119677 | | 1994 | 0.78557124549707 | | 1993 | 0.82019013706223 | | 1992 | 0.87233542607998 | | 1991 | 0.82329824620547 |
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