| Year | Value | | 2019 | 3,554 | | 2018 | 3,415 | | 2017 | 3,303 | | 2016 | 3,227 | | 2015 | 3,198 | | 2014 | 3,291 | | 2013 | 3,425 | | 2012 | 3,592 | | 2011 | 3,748 | | 2010 | 3,857 | | 2009 | 3,955 | | 2008 | 3,938 | | 2007 | 3,810 | | 2006 | 3,631 | | 2005 | 3,469 | | 2004 | 3,542 | | 2003 | 3,613 | | 2002 | 3,641 | | 2001 | 3,607 | | 2000 | 3,541 | | 1999 | 3,622 | | 1998 | 3,775 | | 1997 | 3,947 | | 1996 | 4,077 | | 1995 | 4,123 | | 1994 | 4,249 | | 1993 | 4,259 | | 1992 | 4,160 | | 1991 | 4,003 | | 1990 | 3,818 | | 1989 | 3,633 | | 1988 | 3,442 | | 1987 | 3,233 | | 1986 | 3,026 | | 1985 | 2,856 | | 1984 | 2,879 | | 1983 | 2,923 | | 1982 | 2,935 | | 1981 | 2,897 | | 1980 | 2,827 | | 1979 | 2,836 | | 1978 | 2,851 | | 1977 | 2,847 | | 1976 | 2,804 | | 1975 | 2,722 | | 1974 | 2,754 | | 1973 | 2,771 | | 1972 | 2,765 | | 1971 | 2,740 | | 1970 | 2,705 | | 1969 | 2,699 | | 1968 | 2,708 | | 1967 | 2,722 | | 1966 | 2,723 | | 1965 | 2,699 | | 1964 | 2,602 | | 1963 | 2,484 | | 1962 | 2,355 | | 1961 | 2,236 | | 1960 | 2,137 |
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