| Year | Value | | 2018 | 1,920 | | 2017 | 1,872 | | 2016 | 1,792 | | 2015 | 1,690 | | 2014 | 1,706 | | 2013 | 1,693 | | 2012 | 1,650 | | 2011 | 1,583 | | 2010 | 1,489 | | 2009 | 1,508 | | 2008 | 1,500 | | 2007 | 1,469 | | 2006 | 1,408 | | 2005 | 1,325 | | 2004 | 1,346 | | 2003 | 1,341 | | 2002 | 1,310 | | 2001 | 1,256 | | 2000 | 1,176 | | 1999 | 1,187 | | 1998 | 1,172 | | 1997 | 1,132 | | 1996 | 1,073 | | 1995 | 997 | | 1994 | 997 | | 1993 | 974 | | 1992 | 933 | | 1991 | 876 | | 1990 | 806 | | 1989 | 801 | | 1988 | 780 | | 1987 | 744 | | 1986 | 695 | | 1985 | 636 | | 1984 | 638 | | 1983 | 625 | | 1982 | 605 | | 1981 | 574 | | 1980 | 527 | | 1979 | 529 | | 1978 | 517 | | 1977 | 498 | | 1976 | 472 | | 1975 | 434 | | 1974 | 446 | | 1973 | 448 | | 1972 | 438 | | 1971 | 419 | | 1970 | 394 | | 1969 | 412 | | 1968 | 421 | | 1967 | 416 | | 1966 | 402 | | 1965 | 379 | | 1964 | 405 | | 1963 | 416 | | 1962 | 414 | | 1961 | 399 | | 1960 | 374 |
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