| Year | Value | | 2021 | 3,106 | | 2020 | 2,497.4 | | 2019 | 7,062 | | 2016 | 1,170 | | 2015 | 1,421 | | 2014 | 1,584 | | 2013 | 1,908 | | 2012 | 2,303 | | 2011 | 2,286 | | 2010 | 1,552 | | 1999 | 400 | | 1998 | 1,400 | | 1997 | 1,400 | | 1996 | 1,300 | | 1995 | 2,800 | | 1994 | 3,000 | | 1993 | 3,900 | | 1992 | 4,300 | | 1991 | 4,500 | | 1990 | 9,500 | | 1989 | 6,000 | | 1988 | 6,100 | | 1987 | 5,300 | | 1986 | 6,200 | | 1985 | 6,800 | | 1984 | 6,800 | | 1983 | 6,100 | | 1982 | 5,600 | | 1981 | 4,300 | | 1980 | 5,000 | | 1979 | 5,900 | | 1978 | 10,700 | | 1977 | 11,300 | | 1976 | 10,000 | | 1975 | 3,700 | | 1974 | 4,200 | | 1973 | 4,200 | | 1972 | 3,900 | | 1971 | 3,900 | | 1970 | 8,600 |
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