| Year | Value | | 2021 | 18.36186366 | | 2020 | 1.242318 | | 2019 | 8.30683 | | 2018 | 4.7421655983553 | | 2017 | 4.8339355006997 | | 2016 | 5.065285902 | | 2015 | 3.3857879 | | 2014 | 3.90162 | | 2013 | 2.861556 | | 2012 | 3.8298750405483 | | 2011 | 3.53038 | | 2010 | 2.06226 | | 2009 | 2.614 | | 2008 | 2.83 | | 2007 | 2.867 | | 2006 | 2.788 | | 2005 | 2.722 | | 2004 | 2.463 | | 2003 | 2.078 | | 2002 | 1.988 | | 2001 | 0.882 | | 2000 | 0.774 | | 1999 | 6.1999998093 | | 1998 | 6.5999999046 | | 1997 | 7.5999999046 | | 1996 | 1.2000000477 | | 1995 | 1.2000000477 | | 1994 | 1.1000000238 | | 1993 | 1.1000000238 | | 1992 | 1.1000000238 | | 1991 | 1.1000000238 | | 1990 | 1.1000000238 | | 1989 | 1 | | 1988 | 2.5 | | 1987 | 2.5 | | 1986 | 2.4000000954 | | 1985 | 2.2999999523 | | 1984 | 2.2999999523 | | 1983 | 1.6000000238 | | 1982 | 1.7000000477 | | 1981 | 1.5 | | 1980 | 1.5 | | 1979 | 1.2999999523 | | 1978 | 1.2000000477 | | 1977 | 1.2000000477 | | 1976 | 1.1000000238 | | 1975 | 1.1000000238 | | 1974 | 1.7999999523 | | 1973 | 2.2000000477 | | 1972 | 2.0999999046 | | 1971 | 2 | | 1970 | 1.7999999523 |
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