Year | Value | 2021 | 2.889 | 2020 | 2.942 | 2019 | 2.988 | 2018 | 3.023 | 2017 | 3.05 | 2016 | 3.051 | 2015 | 3.041 | 2014 | 3.004 | 2013 | 2.957 | 2012 | 2.956 | 2011 | 2.88 | 2010 | 2.843 | 2009 | 2.813 | 2008 | 2.753 | 2007 | 2.677 | 2006 | 2.604 | 2005 | 2.555 | 2004 | 2.512 | 2003 | 2.481 | 2002 | 2.456 | 2001 | 2.507 | 2000 | 2.566 | 1999 | 2.624 | 1998 | 2.712 | 1997 | 2.897 | 1996 | 3.136 | 1995 | 3.456 | 1994 | 3.846 | 1993 | 4.059 | 1992 | 4.257 | 1991 | 4.386 | 1990 | 4.556 | 1989 | 4.826 | 1988 | 5.059 | 1987 | 5.327 | 1986 | 5.625 | 1985 | 5.975 | 1984 | 6.219 | 1983 | 6.436 | 1982 | 6.635 | 1981 | 6.808 | 1980 | 6.952 | 1979 | 7.059 | 1978 | 7.14 | 1977 | 7.23 | 1976 | 7.306 | 1975 | 7.373 | 1974 | 7.44 | 1973 | 7.491 | 1972 | 7.546 | 1971 | 7.6 | 1970 | 7.635 | 1969 | 7.653 | 1968 | 7.655 | 1967 | 7.667 | 1966 | 7.672 | 1965 | 7.679 | 1964 | 7.673 | 1963 | 7.649 | 1962 | 7.607 | 1961 | 7.564 | 1960 | 7.503 |
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