| Year | Value | | 2021 | 2.47546368 | | 2020 | 2.47546368 | | 2018 | 3.27 | | 2009 | 26.419 | | 2008 | 33.024 | | 2007 | 40.52 | | 2006 | 66.111 | | 2005 | 66.812 | | 2004 | 59.738 | | 2003 | 48.689 | | 2002 | 36.486 | | 2001 | 32.213 | | 2000 | 32.002 | | 1999 | 21.3999996185 | | 1998 | 11.6000003815 | | 1997 | 16.3999996185 | | 1996 | 9.1000003815 | | 1995 | 4.4000000954 | | 1994 | 10.8000001907 | | 1993 | 9.8999996185 | | 1992 | 9 | | 1991 | 6.5999999046 | | 1990 | 11.5 | | 1989 | 12.8000001907 | | 1988 | 12.1000003815 | | 1987 | 10 | | 1986 | 10.3999996185 | | 1985 | 9.3000001907 | | 1984 | 7.8000001907 | | 1983 | 2.2000000477 | | 1982 | 3 | | 1981 | 0.6000000238 | | 1980 | 0.6000000238 | | 1979 | 0.6000000238 | | 1978 | 0.6000000238 | | 1977 | 0.5 | | 1976 | 0.400000006 | | 1975 | 0.200000003 | | 1974 | 0.1000000015 | | 1973 | 0.1000000015 | | 1972 | 0.1000000015 | | 1971 | 0.1000000015 | | 1970 | 0.1000000015 |
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