| Year | Value | | 2021 | 3,312.786 | | 2020 | 3,751.74 | | 2019 | 4,388 | | 2018 | 5,005 | | 2017 | 5,005 | | 1998 | 3,200 | | 1997 | 3,100 | | 1996 | 3,100 | | 1995 | 3,000 | | 1994 | 2,900 | | 1993 | 2,900 | | 1992 | 2,900 | | 1991 | 2,900 | | 1990 | 2,900 | | 1989 | 3,000 | | 1988 | 3,000 | | 1987 | 3,000 | | 1986 | 3,400 | | 1985 | 4,200 | | 1984 | 7,100 | | 1983 | 6,700 | | 1982 | 6,600 | | 1981 | 6,600 |
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