Year | Value | 2021 | 6.776 | 2020 | 6.616 | 2019 | 6.439 | 2018 | 6.569 | 2017 | 6.767 | 2016 | 6.93 | 2015 | 7.208 | 2014 | 7.502 | 2013 | 7.734 | 2012 | 8.119 | 2011 | 8.52 | 2010 | 9.001 | 2009 | 9.485 | 2008 | 10.143 | 2007 | 10.807 | 2006 | 11.539 | 2005 | 12.226 | 2004 | 12.745 | 2003 | 13.258 | 2002 | 13.96 | 2001 | 14.36 | 2000 | 14.758 | 1999 | 15.539 | 1998 | 15.413 | 1997 | 15.808 | 1996 | 16.317 | 1995 | 16.892 | 1994 | 17.345 | 1993 | 17.808 | 1992 | 18.295 | 1991 | 18.88 | 1990 | 20.055 | 1989 | 19.762 | 1988 | 19.782 | 1987 | 19.495 | 1986 | 26.357 | 1985 | 26.791 | 1984 | 27.792 | 1983 | 28.374 | 1982 | 21.04 | 1981 | 21.183 | 1980 | 21.487 | 1979 | 21.802 | 1978 | 22.532 | 1977 | 22.538 | 1976 | 22.487 | 1975 | 24.881 | 1974 | 24.867 | 1973 | 22.879 | 1972 | 22.978 | 1971 | 21.792 | 1970 | 21.818 | 1969 | 21.756 | 1968 | 21.664 | 1967 | 21.713 | 1966 | 23.934 | 1965 | 21.878 | 1964 | 21.959 | 1963 | 22.174 | 1962 | 22.573 | 1961 | 22.865 | 1960 | 23.349 |
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