| Year | Value | | 2024 | 2.9622029442049 | | 2023 | 2.9046801706116 | | 2022 | 1.8039045748818 | | 2021 | 0.55390242238689 | | 2020 | 1.0843689711322 | | 2019 | 1.4617125993813 | | 2018 | 1.4332261567935 | | 2017 | 1.1954357545155 | | 2016 | 1.13153974027 | | 2015 | 0.76030014523894 | | 2014 | 1.0014228468966 | | 2013 | 1.0533809805532 | | 2012 | 1.0837465223365 | | 2011 | 0.97540725097113 | | 2010 | 1.1113520297169 | | 2009 | 1.1447076847653 | | 2008 | 1.083871149194 | | 2007 | 0.97065417331665 | | 2006 | 1.0135593914496 | | 2005 | 0.94708626967041 | | 2004 | 0.93218696414805 | | 2003 | 0.89922680999867 | | 2002 | 1.0847932832952 | | 2001 | 1.0861994547665 | | 2000 | 0.93128155345243 | | 1999 | 0.81284262371617 | | 1998 | 0.82990935332374 | | 1997 | 0.99378859146519 | | 1996 | 1.0453117831183 | | 1995 | 1.0347694838683 | | 1994 | 1.0952581070613 | | 1993 | 1.0989308788788 | | 1992 | 1.1836755413894 | | 1991 | 1.2427612313168 | | 1990 | 1.5076606728481 | | 1989 | 1.7941935149194 | | 1988 | 1.29662488996 | | 1987 | 1.318167781745 | | 1986 | 0.99404015063097 | | 1985 | 0.91377427539001 | | 1984 | 0.94403471604109 | | 1983 | 0.98848756714777 | | 1982 | 1.1896243407757 | | 1981 | 1.2333972548053 | | 1980 | 1.2895949784716 | | 1979 | 0.9896987332347 | | 1978 | 0.99545694441135 | | 1977 | 1.1702568778327 | | 1976 | 1.315806565588 |
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