| Year | Value | | 2018 | 5,967 | | 2017 | 5,766 | | 2016 | 5,529 | | 2015 | 5,174 | | 2014 | 4,621 | | 2013 | 3,955 | | 2012 | 3,259 | | 2011 | 2,675 | | 2010 | 2,298 | | 2009 | 2,149 | | 2008 | 2,135 | | 2007 | 2,200 | | 2006 | 2,309 | | 2005 | 2,470 | | 2004 | 2,666 | | 2003 | 2,973 | | 2002 | 3,336 | | 2001 | 3,664 | | 2000 | 3,886 | | 1999 | 4,026 | | 1998 | 4,057 | | 1997 | 4,006 | | 1996 | 3,938 | | 1995 | 3,898 | | 1994 | 3,857 | | 1993 | 3,839 | | 1992 | 3,825 | | 1991 | 3,781 | | 1990 | 3,679 | | 1989 | 3,439 | | 1988 | 3,116 | | 1987 | 2,753 | | 1986 | 2,432 | | 1985 | 2,214 | | 1984 | 2,081 | | 1983 | 2,075 | | 1982 | 2,166 | | 1981 | 2,286 | | 1980 | 2,398 | | 1979 | 2,509 | | 1978 | 2,595 | | 1977 | 2,674 | | 1976 | 2,774 | | 1975 | 2,924 | | 1974 | 3,088 | | 1973 | 3,307 | | 1972 | 3,537 | | 1971 | 3,696 | | 1970 | 3,712 | | 1969 | 3,653 | | 1968 | 3,425 | | 1967 | 3,091 | | 1966 | 2,770 | | 1965 | 2,544 | | 1964 | 2,368 | | 1963 | 2,298 | | 1962 | 2,303 | | 1961 | 2,305 | | 1960 | 2,250 |
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