| Year | Value | | 2021 | 3,116 | | 2020 | 3,116 | | 2019 | 3,128 | | 2018 | 3,135 | | 2017 | 3,142 | | 2016 | 3,149 | | 2015 | 3,156 | | 2014 | 3,163 | | 2013 | 3,170 | | 2012 | 3,177 | | 2011 | 3,184 | | 2010 | 3,191 | | 2009 | 3,198 | | 2008 | 3,254 | | 2007 | 3,312 | | 2006 | 3,370 | | 2005 | 3,428 | | 2004 | 3,486 | | 2003 | 3,544 | | 2002 | 3,602 | | 2001 | 3,660 | | 2000 | 3,718 | | 1999 | 3,776 | | 1998 | 3,834 | | 1997 | 3,892 | | 1996 | 3,950 | | 1995 | 4,008 | | 1994 | 4,066 | | 1993 | 4,124 | | 1992 | 4,182 | | 1991 | 4,240 | | 1990 | 4,100 | | 1989 | 3,950 | | 1988 | 3,800 | | 1987 | 3,650 | | 1986 | 3,500 | | 1985 | 3,450 | | 1984 | 3,300 | | 1983 | 3,200 | | 1982 | 3,100 | | 1981 | 3,000 | | 1980 | 2,900 | | 1979 | 2,850 | | 1978 | 2,800 | | 1977 | 2,700 | | 1976 | 2,600 | | 1975 | 2,450 | | 1974 | 2,400 | | 1973 | 2,350 | | 1972 | 2,300 | | 1971 | 2,210 | | 1970 | 2,210 | | 1969 | 2,210 | | 1968 | 2,190 | | 1967 | 2,210 | | 1966 | 2,230 | | 1965 | 2,230 | | 1964 | 2,280 | | 1963 | 2,280 | | 1962 | 2,270 | | 1961 | 2,270 |
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