Year | Value | 2021 | 6.799 | 2020 | 6.67 | 2019 | 6.586 | 2018 | 6.647 | 2017 | 6.728 | 2016 | 6.974 | 2015 | 7.012 | 2014 | 7.143 | 2013 | 7.36 | 2012 | 7.312 | 2011 | 7.541 | 2010 | 7.648 | 2009 | 7.787 | 2008 | 8.381 | 2007 | 8.319 | 2006 | 8.705 | 2005 | 10.065 | 2004 | 10.325 | 2003 | 9.677 | 2002 | 9.34 | 2001 | 9.56 | 2000 | 9.699 | 1999 | 10.337 | 1998 | 14.803 | 1997 | 12.566 | 1996 | 12.94 | 1995 | 13.189 | 1994 | 10.879 | 1993 | 16.68 | 1992 | 17.206 | 1991 | 14.501 | 1990 | 14.831 | 1989 | 15.118 | 1988 | 25.865 | 1987 | 19.307 | 1986 | 14.094 | 1985 | 17.679 | 1984 | 17.913 | 1983 | 17.231 | 1982 | 12.817 | 1981 | 12.969 | 1980 | 13.08 | 1979 | 13.307 | 1978 | 13.408 | 1977 | 13.348 | 1976 | 13.488 | 1975 | 13.592 | 1974 | 13.742 | 1973 | 13.893 | 1972 | 15.715 | 1971 | 15.972 | 1970 | 18.502 | 1969 | 18.799 | 1968 | 18.608 | 1967 | 18.918 | 1966 | 19.239 | 1965 | 17.755 | 1964 | 16.259 | 1963 | 18.276 | 1962 | 17.538 | 1961 | 17.767 | 1960 | 18.09 |
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