| Year | Value | | 2021 | 46,390.423 | | 2020 | 56,299.058 | | 2019 | 65,846.852 | | 2018 | 66,567 | | 2017 | 66,567 | | 1998 | 28,300 | | 1997 | 28,400 | | 1996 | 28,400 | | 1995 | 26,900 | | 1994 | 25,600 | | 1993 | 25,600 | | 1992 | 25,400 | | 1991 | 24,900 | | 1990 | 24,900 | | 1989 | 24,900 | | 1988 | 24,000 | | 1987 | 24,900 | | 1986 | 32,000 | | 1985 | 26,400 | | 1984 | 65,500 | | 1983 | 60,000 | | 1982 | 60,000 | | 1981 | 59,000 |
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