| Year | Value | | 2021 | 0.312 | | 2020 | 0.478 | | 2019 | 1.842301 | | 2018 | 1.970266 | | 2017 | 1.857094 | | 2016 | 1.774534 | | 2015 | 1.641624 | | 2014 | 2.085996 | | 1995 | 6.8000001907 | | 1994 | 11.6999998093 | | 1993 | 24.1000003815 | | 1992 | 22.2999992371 | | 1991 | 5.0999999046 | | 1990 | 4.5 | | 1989 | 3.9000000954 | | 1988 | 7 | | 1987 | 15.1000003815 | | 1986 | 13.6999998093 | | 1985 | 3.0999999046 | | 1984 | 3 | | 1983 | 2.7000000477 | | 1982 | 2.7000000477 | | 1981 | 2.9000000954 | | 1980 | 2.5999999046 | | 1979 | 2.4000000954 | | 1978 | 2.2999999523 | | 1977 | 2.0999999046 | | 1976 | 1 | | 1975 | 1 | | 1974 | 1 | | 1973 | 1 | | 1972 | 1.1000000238 | | 1971 | 0.8000000119 | | 1970 | 0.6999999881 |
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