| Year | Value | | 2021 | 75.18520667 | | 2020 | 69.97121783064 | | 2019 | 79.335 | | 2018 | 75.077397732 | | 2017 | 81.557609650439 | | 2016 | 80.352946998651 | | 2015 | 79.382095832289 | | 2014 | 83.431251799322 | | 2013 | 93.432544535186 | | 2003 | 0.031 | | 2002 | 0.028 | | 2001 | 0.028 | | 2000 | 0.457 | | 1999 | 0.400000006 | | 1998 | 0.5 | | 1997 | 0.5 | | 1994 | 15.6999998093 | | 1993 | 13.6000003815 | | 1992 | 16.5 | | 1991 | 21.7000007629 | | 1990 | 29.6000003815 | | 1989 | 24.8999996185 | | 1988 | 24.7999992371 | | 1987 | 25.7000007629 | | 1986 | 24.5 | | 1985 | 25.2999992371 | | 1984 | 25.2999992371 | | 1983 | 23.3999996185 | | 1982 | 22.8999996185 | | 1981 | 17.5 | | 1980 | 46.9000015259 | | 1979 | 78.9000015259 | | 1978 | 36.2000007629 | | 1977 | 32.5999984741 | | 1976 | 18.2000007629 | | 1975 | 19 | | 1974 | 21.5 | | 1973 | 15.5 | | 1972 | 5.8000001907 | | 1971 | 5.4000000954 | | 1970 | 4.5 |
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