| Year | Value | | 2000 | 61,031 | | 1999 | 58,700 | | 1998 | 51,100 | | 1997 | 51,300 | | 1996 | 51,300 | | 1995 | 48,200 | | 1994 | 43,800 | | 1993 | 34,000 | | 1992 | 159,200 | | 1991 | 129,600 | | 1990 | 129,600 | | 1989 | 109,500 | | 1988 | 86,500 | | 1987 | 85,000 | | 1986 | 80,900 | | 1985 | 90,000 | | 1984 | 85,000 | | 1983 | 95,000 | | 1982 | 100,000 | | 1981 | 97,000 | | 1980 | 115,000 | | 1979 | 145,000 | | 1978 | 110,000 | | 1977 | 110,000 | | 1976 | 89,000 | | 1975 | 85,000 | | 1974 | 81,000 | | 1973 | 77,500 | | 1972 | 144,000 | | 1971 | 137,500 | | 1970 | 107,100 |
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