| Year | Value | | 2018 | 1,703 | | 2017 | 1,903 | | 2016 | 2,104 | | 2015 | 2,280 | | 2014 | 2,424 | | 2013 | 2,515 | | 2012 | 2,565 | | 2011 | 2,584 | | 2010 | 2,582 | | 2009 | 2,537 | | 2008 | 2,473 | | 2007 | 2,394 | | 2006 | 2,305 | | 2005 | 2,202 | | 2004 | 2,028 | | 2003 | 1,855 | | 2002 | 1,683 | | 2001 | 1,527 | | 2000 | 1,404 | | 1999 | 1,289 | | 1998 | 1,239 | | 1997 | 1,245 | | 1996 | 1,273 | | 1995 | 1,288 | | 1994 | 1,298 | | 1993 | 1,294 | | 1992 | 1,279 | | 1991 | 1,267 | | 1990 | 1,271 | | 1989 | 1,272 | | 1988 | 1,302 | | 1987 | 1,350 | | 1986 | 1,390 | | 1985 | 1,396 | | 1984 | 1,376 | | 1983 | 1,297 | | 1982 | 1,165 | | 1981 | 1,022 | | 1980 | 904 | | 1979 | 825 | | 1978 | 791 | | 1977 | 792 | | 1976 | 799 | | 1975 | 780 | | 1974 | 761 | | 1973 | 717 | | 1972 | 651 | | 1971 | 583 | | 1970 | 530 | | 1969 | 529 | | 1968 | 563 | | 1967 | 628 | | 1966 | 700 | | 1965 | 757 | | 1964 | 812 | | 1963 | 851 | | 1962 | 872 | | 1961 | 888 | | 1960 | 899 |
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