| Year | Value | | 2018 | 12,826 | | 2017 | 12,828 | | 2016 | 12,723 | | 2015 | 12,467 | | 2014 | 12,005 | | 2013 | 11,339 | | 2012 | 10,554 | | 2011 | 9,802 | | 2010 | 9,176 | | 2009 | 8,718 | | 2008 | 8,392 | | 2007 | 8,132 | | 2006 | 7,792 | | 2005 | 7,269 | | 2004 | 6,607 | | 2003 | 5,784 | | 2002 | 4,920 | | 2001 | 4,202 | | 2000 | 3,749 | | 1999 | 3,571 | | 1998 | 3,608 | | 1997 | 3,796 | | 1996 | 4,036 | | 1995 | 4,264 | | 1994 | 4,571 | | 1993 | 4,921 | | 1992 | 5,276 | | 1991 | 5,586 | | 1990 | 5,820 | | 1989 | 5,833 | | 1988 | 5,795 | | 1987 | 5,734 | | 1986 | 5,699 | | 1985 | 5,709 | | 1984 | 5,720 | | 1983 | 5,731 | | 1982 | 5,710 | | 1981 | 5,594 | | 1980 | 5,345 | | 1979 | 5,009 | | 1978 | 4,529 | | 1977 | 3,993 | | 1976 | 3,548 | | 1975 | 3,282 | | 1974 | 3,162 | | 1973 | 3,228 | | 1972 | 3,427 | | 1971 | 3,651 | | 1970 | 3,818 | | 1969 | 3,993 | | 1968 | 4,119 | | 1967 | 4,217 | | 1966 | 4,346 | | 1965 | 4,541 | | 1964 | 4,738 | | 1963 | 5,002 | | 1962 | 5,277 | | 1961 | 5,451 | | 1960 | 5,451 |
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