Year | Value | 2021 | 6.28 | 2020 | 5.998 | 2019 | 6.137 | 2018 | 6.227 | 2017 | 6.367 | 2016 | 6.49 | 2015 | 6.724 | 2014 | 6.953 | 2013 | 7.285 | 2012 | 7.604 | 2011 | 7.814 | 2010 | 8.068 | 2009 | 8.284 | 2008 | 8.64 | 2007 | 9.186 | 2006 | 9.803 | 2005 | 10.546 | 2004 | 11.546 | 2003 | 12.791 | 2002 | 13.926 | 2001 | 14.833 | 2000 | 15.774 | 1999 | 17.121 | 1998 | 18.779 | 1997 | 19.637 | 1996 | 19.68 | 1995 | 20.369 | 1994 | 103.534 | 1993 | 19.436 | 1992 | 17.877 | 1991 | 16.453 | 1990 | 15.403 | 1989 | 14.554 | 1988 | 14.328 | 1987 | 14.281 | 1986 | 14.431 | 1985 | 14.649 | 1984 | 14.982 | 1983 | 15.427 | 1982 | 16.063 | 1981 | 17.073 | 1980 | 18.199 | 1979 | 19.211 | 1978 | 20.065 | 1977 | 20.543 | 1976 | 20.591 | 1975 | 20.422 | 1974 | 19.926 | 1973 | 19.414 | 1972 | 18.93 | 1971 | 18.628 | 1970 | 18.352 | 1969 | 18.112 | 1968 | 17.833 | 1967 | 17.603 | 1966 | 17.591 | 1965 | 17.619 | 1964 | 17.786 | 1963 | 20.578 | 1962 | 18.301 | 1961 | 18.693 | 1960 | 19.195 |
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