Year | Value | 2021 | 8.141 | 2020 | 8.281 | 2019 | 7.824 | 2018 | 8.061 | 2017 | 8.239 | 2016 | 8.512 | 2015 | 8.799 | 2014 | 9.016 | 2013 | 9.346 | 2012 | 9.718 | 2011 | 10.145 | 2010 | 10.589 | 2009 | 11.206 | 2008 | 11.812 | 2007 | 12.477 | 2006 | 13.174 | 2005 | 13.922 | 2004 | 14.683 | 2003 | 15.543 | 2002 | 16.272 | 2001 | 16.912 | 2000 | 17.431 | 1999 | 17.968 | 1998 | 18.489 | 1997 | 19.074 | 1996 | 19.762 | 1995 | 20.523 | 1994 | 21.405 | 1993 | 22.213 | 1992 | 22.985 | 1991 | 23.667 | 1990 | 24.067 | 1989 | 24.665 | 1988 | 25.124 | 1987 | 25.49 | 1986 | 25.756 | 1985 | 25.813 | 1984 | 25.7 | 1983 | 25.366 | 1982 | 25.281 | 1981 | 25.241 | 1980 | 25.448 | 1979 | 25.671 | 1978 | 26.168 | 1977 | 26.782 | 1976 | 27.34 | 1975 | 27.678 | 1974 | 28.157 | 1973 | 28.376 | 1972 | 28.393 | 1971 | 28.694 | 1970 | 27.929 | 1969 | 27.624 | 1968 | 27.37 | 1967 | 27.134 | 1966 | 27.173 | 1965 | 27.244 | 1964 | 27.275 | 1963 | 27.282 | 1962 | 27.371 | 1961 | 27.444 | 1960 | 27.566 |
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