| Year | Value | | 1994 | 2.5 | | 1993 | 2.7999999523 | | 1992 | 0.8000000119 | | 1991 | 0.6999999881 | | 1990 | 70.4000015259 | | 1988 | 4 | | 1987 | 3 | | 1986 | 5.5999999046 | | 1985 | 8.5 | | 1984 | 9.6999998093 | | 1983 | 7.0999999046 | | 1981 | 11 | | 1980 | 10.8000001907 | | 1979 | 17.5 | | 1978 | 20.6000003815 | | 1977 | 17.5 | | 1976 | 9.5 | | 1975 | 7.6999998093 | | 1974 | 3.5 | | 1973 | 3.5 | | 1972 | 3.2999999523 | | 1971 | 3.2999999523 | | 1970 | 4.1999998093 |
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