| Year | Value | | 2021 | 1,820 | | 2020 | 1,800 | | 2019 | 1,740 | | 2018 | 1,720 | | 2017 | 1,720 | | 2016 | 1,700 | | 2015 | 1,700 | | 2014 | 1,600 | | 2013 | 1,600 | | 2012 | 1,600 | | 2011 | 1,570 | | 2010 | 1,570 | | 2009 | 1,550 | | 2008 | 1,520 | | 2007 | 1,520 | | 2006 | 1,520 | | 2005 | 1,520 | | 2004 | 1,520 | | 2003 | 1,520 | | 2002 | 1,520 | | 2001 | 1,490 | | 2000 | 1,490 | | 1999 | 1,500 | | 1998 | 1,480 | | 1997 | 1,480 | | 1996 | 1,470 | | 1995 | 1,460 | | 1994 | 1,430 | | 1993 | 1,430 | | 1992 | 1,360 | | 1991 | 1,300 | | 1990 | 1,260 | | 1989 | 1,200 | | 1988 | 1,150 | | 1987 | 1,120 | | 1986 | 1,030 | | 1985 | 1,010 | | 1984 | 970 | | 1983 | 970 | | 1982 | 970 | | 1981 | 970 | | 1980 | 960 | | 1979 | 940 | | 1978 | 930 | | 1977 | 860 | | 1976 | 850 | | 1975 | 850 | | 1974 | 840 | | 1973 | 840 | | 1972 | 830 | | 1971 | 830 | | 1970 | 820 | | 1969 | 820 | | 1968 | 810 | | 1967 | 810 | | 1966 | 810 | | 1965 | 800 | | 1964 | 800 | | 1963 | 800 | | 1962 | 790 | | 1961 | 790 |
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