| Year | Value | | 2022 | 0.79013916658833 | | 2021 | 0.72229820205617 | | 2020 | 0.28829020228429 | | 2019 | 0.18943275806294 | | 2018 | 0.25170388232479 | | 2017 | 0.27661748770087 | | 2016 | 0.39182598317462 | | 2015 | 0.47380087506927 | | 2014 | 0.43328799977302 | | 2013 | 0.38491876166814 | | 2012 | 0.10134209399598 | | 2011 | 0.2120990218084 | | 2010 | 0.22281586828706 | | 2009 | 0.1980605666238 | | 2008 | 0.27531974126733 | | 2007 | 0.42099785901555 | | 2006 | 0.5259119961548 | | 2005 | 0.56676739159051 | | 2004 | 0.59776922362822 | | 2003 | 0.58209506672376 | | 2002 | 0.57387580569395 | | 2001 | 0.58985755025645 | | 2000 | 0.60708449520079 | | 1999 | 0.62855241981038 | | 1998 | 0.6782170639828 | | 1997 | 0.46103450792304 | | 1996 | 0.21781276720722 | | 1995 | 0.24635980974319 | | 1994 | 0.23993225145212 | | 1993 | 0.23345687627873 | | 1992 | 0.25218150248715 | | 1991 | 0.28623898736679 | | 1990 | 0.35310986128376 | | 1989 | 0.44825307587292 | | 1988 | 0.56007641376201 | | 1987 | 0.32292926711022 | | 1986 | 0.023695095741187 | | 1985 | 0.034007121212749 | | 1984 | 0.042267388246988 | | 1983 | 0.051569785374912 | | 1982 | 0.087729715551059 | | 1981 | 0.14259588888229 | | 1980 | 0.20909465524888 | | 1979 | 0.28951990046915 | | 1978 | 0.39568134759001 | | 1977 | 0.97082033976997 | | 1976 | 1.5329549970098 | | 1975 | 1.58507556184 | | 1974 | 1.5289042628569 | | 1973 | 1.4854125002016 | | 1972 | 1.5476183567649 | | 1971 | 1.6285884182559 | | 1970 | 1.7343463980487 | | 1969 | 1.8608004835834 | | 1968 | 2.0648004303709 | | 1967 | 2.3911638951193 | | 1966 | 2.6773252700058 | | 1965 | 2.7959792998255 | | 1964 | 2.8232905183503 | | 1963 | 2.8352574783496 | | 1962 | 2.8372611887695 | | 1961 | 2.8696814188012 |
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