Year | Value | 2021 | 2.328 | 2020 | 2.353 | 2019 | 2.382 | 2018 | 2.415 | 2017 | 2.451 | 2016 | 2.451 | 2015 | 2.531 | 2014 | 2.548 | 2013 | 2.594 | 2012 | 2.598 | 2011 | 2.609 | 2010 | 2.586 | 2009 | 2.578 | 2008 | 2.549 | 2007 | 2.55 | 2006 | 2.559 | 2005 | 2.568 | 2004 | 2.598 | 2003 | 2.632 | 2002 | 2.67 | 2001 | 2.715 | 2000 | 2.796 | 1999 | 2.871 | 1998 | 3.009 | 1997 | 3.12 | 1996 | 3.219 | 1995 | 3.33 | 1994 | 3.468 | 1993 | 3.612 | 1992 | 3.806 | 1991 | 3.937 | 1990 | 4.018 | 1989 | 4.139 | 1988 | 4.327 | 1987 | 4.538 | 1986 | 4.746 | 1985 | 4.96 | 1984 | 5.154 | 1983 | 5.354 | 1982 | 5.552 | 1981 | 5.652 | 1980 | 5.734 | 1979 | 5.802 | 1978 | 5.874 | 1977 | 5.998 | 1976 | 6.139 | 1975 | 6.271 | 1974 | 6.373 | 1973 | 6.465 | 1972 | 6.533 | 1971 | 6.61 | 1970 | 6.675 | 1969 | 6.72 | 1968 | 6.782 | 1967 | 6.844 | 1966 | 6.895 | 1965 | 6.93 | 1964 | 6.969 | 1963 | 7 | 1962 | 7.088 | 1961 | 7.072 | 1960 | 7.04 |
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