| Year | Value | | 1996 | 81 | | 1995 | 357 | | 1994 | 424 | | 1993 | 506 | | 1992 | 600 | | 1991 | 707 | | 1990 | 830 | | 1989 | 972 | | 1988 | 1,132 | | 1987 | 1,322 | | 1986 | 1,539 | | 1985 | 1,792 | | 1984 | 2,091 | | 1983 | 2,439 | | 1982 | 2,852 | | 1981 | 3,345 | | 1980 | 3,633 | | 1979 | 3,905 | | 1978 | 4,198 | | 1977 | 4,512 | | 1976 | 4,847 | | 1975 | 5,208 | | 1974 | 5,593 | | 1973 | 6,015 | | 1972 | 6,473 | | 1971 | 6,975 | | 1970 | 7,339 | | 1969 | 7,508 | | 1968 | 7,652 | | 1967 | 7,781 | | 1966 | 7,896 | | 1965 | 8,001 | | 1964 | 8,095 | | 1963 | 8,184 | | 1962 | 8,268 | | 1961 | 8,348 | | 1960 | 8,339 |
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