Year | Value | 2021 | 2.667 | 2020 | 2.701 | 2019 | 2.74 | 2018 | 2.786 | 2017 | 2.836 | 2016 | 2.887 | 2015 | 2.93 | 2014 | 2.956 | 2013 | 2.958 | 2012 | 2.936 | 2011 | 2.892 | 2010 | 2.833 | 2009 | 2.769 | 2008 | 2.712 | 2007 | 2.676 | 2006 | 2.665 | 2005 | 2.658 | 2004 | 2.648 | 2003 | 2.665 | 2002 | 2.686 | 2001 | 2.791 | 2000 | 2.898 | 1999 | 2.995 | 1998 | 3.102 | 1997 | 3.213 | 1996 | 3.336 | 1995 | 3.507 | 1994 | 3.67 | 1993 | 3.837 | 1992 | 3.962 | 1991 | 4.106 | 1990 | 4.243 | 1989 | 4.447 | 1988 | 4.62 | 1987 | 4.8 | 1986 | 4.861 | 1985 | 4.885 | 1984 | 4.872 | 1983 | 4.926 | 1982 | 4.975 | 1981 | 5.11 | 1980 | 5.253 | 1979 | 5.403 | 1978 | 5.535 | 1977 | 5.683 | 1976 | 5.802 | 1975 | 5.904 | 1974 | 6.015 | 1973 | 6.109 | 1972 | 6.19 | 1971 | 6.323 | 1970 | 6.404 | 1969 | 6.482 | 1968 | 6.56 | 1967 | 6.635 | 1966 | 6.703 | 1965 | 6.756 | 1964 | 6.787 | 1963 | 6.788 | 1962 | 6.756 | 1961 | 6.689 | 1960 | 6.59 |
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