| Year | Value | | 2019 | 3,260 | | 2018 | 3,328 | | 2017 | 3,407 | | 2016 | 3,471 | | 2015 | 3,508 | | 2014 | 3,500 | | 2013 | 3,481 | | 2012 | 3,469 | | 2011 | 3,486 | | 2010 | 3,534 | | 2009 | 3,490 | | 2008 | 3,433 | | 2007 | 3,376 | | 2006 | 3,323 | | 2005 | 3,284 | | 2004 | 3,266 | | 2003 | 3,257 | | 2002 | 3,256 | | 2001 | 3,227 | | 2000 | 3,135 | | 1999 | 3,132 | | 1998 | 3,040 | | 1997 | 2,888 | | 1996 | 2,747 | | 1995 | 2,660 | | 1994 | 2,638 | | 1993 | 2,619 | | 1992 | 2,592 | | 1991 | 2,541 | | 1990 | 2,464 | | 1989 | 2,467 | | 1988 | 2,484 | | 1987 | 2,508 | | 1986 | 2,531 | | 1985 | 2,552 | | 1984 | 2,570 | | 1983 | 2,573 | | 1982 | 2,571 | | 1981 | 2,572 | | 1980 | 2,579 | | 1979 | 2,564 | | 1978 | 2,527 | | 1977 | 2,477 | | 1976 | 2,425 | | 1975 | 2,376 | | 1974 | 2,391 | | 1973 | 2,407 | | 1972 | 2,418 | | 1971 | 2,420 | | 1970 | 2,396 | | 1969 | 2,385 | | 1968 | 2,348 | | 1967 | 2,292 | | 1966 | 2,236 | | 1965 | 2,191 | | 1964 | 2,129 | | 1963 | 2,075 | | 1962 | 2,028 | | 1961 | 1,979 | | 1960 | 1,931 |
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