Year | Value | 2021 | 6.983 | 2020 | 6.706 | 2019 | 6.611 | 2018 | 6.955 | 2017 | 7.149 | 2016 | 7.541 | 2015 | 8.005 | 2014 | 8.376 | 2013 | 9.081 | 2012 | 9.783 | 2011 | 10.608 | 2010 | 11.412 | 2009 | 12.183 | 2008 | 12.96 | 2007 | 13.496 | 2006 | 13.951 | 2005 | 14.633 | 2004 | 15.541 | 2003 | 16.573 | 2002 | 17.66 | 2001 | 18.588 | 2000 | 19.559 | 1999 | 20.175 | 1998 | 20.823 | 1997 | 20.657 | 1996 | 20.459 | 1995 | 20.333 | 1994 | 20.623 | 1993 | 21.012 | 1992 | 21.289 | 1991 | 21.711 | 1990 | 22.087 | 1989 | 22.492 | 1988 | 22.892 | 1987 | 22.275 | 1986 | 22.032 | 1985 | 21.653 | 1984 | 21.219 | 1983 | 20.875 | 1982 | 20.861 | 1981 | 21.025 | 1980 | 21.403 | 1979 | 21.895 | 1978 | 22.559 | 1977 | 23.441 | 1976 | 24.29 | 1975 | 25.166 | 1974 | 26.04 | 1973 | 26.768 | 1972 | 27.436 | 1971 | 28.117 | 1970 | 28.662 | 1969 | 29.087 | 1968 | 29.366 | 1967 | 29.483 | 1966 | 29.5 | 1965 | 29.611 | 1964 | 29.631 | 1963 | 29.669 | 1962 | 29.547 | 1961 | 29.729 | 1960 | 29.739 |
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