| Year | Value | | 2018 | 16,137 | | 2017 | 15,671 | | 2016 | 15,238 | | 2015 | 14,836 | | 2014 | 14,431 | | 2013 | 14,046 | | 2012 | 13,677 | | 2011 | 13,324 | | 2010 | 12,985 | | 2009 | 12,631 | | 2008 | 12,284 | | 2007 | 11,939 | | 2006 | 11,591 | | 2005 | 11,239 | | 2004 | 10,856 | | 2003 | 10,468 | | 2002 | 10,071 | | 2001 | 9,656 | | 2000 | 9,218 | | 1999 | 8,734 | | 1998 | 8,218 | | 1997 | 7,712 | | 1996 | 7,277 | | 1995 | 6,954 | | 1994 | 6,727 | | 1993 | 6,617 | | 1992 | 6,590 | | 1991 | 6,578 | | 1990 | 6,540 | | 1989 | 6,468 | | 1988 | 6,370 | | 1987 | 6,254 | | 1986 | 6,148 | | 1985 | 6,061 | | 1984 | 5,966 | | 1983 | 5,880 | | 1982 | 5,795 | | 1981 | 5,707 | | 1980 | 5,607 | | 1979 | 5,471 | | 1978 | 5,327 | | 1977 | 5,183 | | 1976 | 5,051 | | 1975 | 4,947 | | 1974 | 4,857 | | 1973 | 4,790 | | 1972 | 4,741 | | 1971 | 4,706 | | 1970 | 4,679 | | 1969 | 4,634 | | 1968 | 4,593 | | 1967 | 4,556 | | 1966 | 4,524 | | 1965 | 4,500 | | 1964 | 4,461 | | 1963 | 4,425 | | 1962 | 4,390 | | 1961 | 4,353 | | 1960 | 4,311 |
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