| Year | Value | | 2019 | 1,068 | | 2018 | 1,038 | | 2017 | 1,008 | | 2016 | 984 | | 2015 | 974 | | 2014 | 930 | | 2013 | 907 | | 2012 | 898 | | 2011 | 903 | | 2010 | 910 | | 2009 | 928 | | 2008 | 949 | | 2007 | 966 | | 2006 | 983 | | 2005 | 998 | | 2004 | 992 | | 2003 | 980 | | 2002 | 966 | | 2001 | 956 | | 2000 | 948 | | 1999 | 952 | | 1998 | 965 | | 1997 | 985 | | 1996 | 1,002 | | 1995 | 1,015 | | 1994 | 980 | | 1993 | 938 | | 1992 | 891 | | 1991 | 847 | | 1990 | 812 | | 1989 | 786 | | 1988 | 764 | | 1987 | 745 | | 1986 | 728 | | 1985 | 716 | | 1984 | 712 | | 1983 | 702 | | 1982 | 685 | | 1981 | 665 | | 1980 | 644 | | 1979 | 611 | | 1978 | 583 | | 1977 | 562 | | 1976 | 548 | | 1975 | 537 | | 1974 | 526 | | 1973 | 521 | | 1972 | 520 | | 1971 | 518 | | 1970 | 514 | | 1969 | 511 | | 1968 | 502 | | 1967 | 491 | | 1966 | 479 | | 1965 | 465 | | 1964 | 444 | | 1963 | 422 | | 1962 | 399 | | 1961 | 380 | | 1960 | 369 |
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