Year | Value | 2021 | 1.809 | 2020 | 1.818 | 2019 | 1.84 | 2018 | 1.845 | 2017 | 1.857 | 2016 | 1.87 | 2015 | 1.884 | 2014 | 1.885 | 2013 | 1.86 | 2012 | 1.836 | 2011 | 1.811 | 2010 | 1.809 | 2009 | 1.951 | 2008 | 1.977 | 2007 | 1.956 | 2006 | 1.958 | 2005 | 1.955 | 2004 | 1.962 | 2003 | 1.914 | 2002 | 1.943 | 2001 | 1.981 | 2000 | 1.969 | 1999 | 1.99 | 1998 | 2.008 | 1997 | 2.031 | 1996 | 2.107 | 1995 | 2.164 | 1994 | 2.203 | 1993 | 2.248 | 1992 | 2.292 | 1991 | 2.34 | 1990 | 2.35 | 1989 | 2.35 | 1988 | 2.414 | 1987 | 2.456 | 1986 | 2.539 | 1985 | 2.582 | 1984 | 2.629 | 1983 | 2.687 | 1982 | 2.763 | 1981 | 2.84 | 1980 | 2.841 | 1979 | 2.849 | 1978 | 2.793 | 1977 | 2.771 | 1976 | 2.836 | 1975 | 3.047 | 1974 | 3.142 | 1973 | 3.353 | 1972 | 3.889 | 1971 | 3.739 | 1970 | 3.848 | 1969 | 3.86 | 1968 | 3.872 | 1967 | 4.05 | 1966 | 3.709 | 1965 | 3.556 | 1964 | 3.547 | 1963 | 3.626 | 1962 | 3.412 | 1961 | 3.261 | 1960 | 3.568 |
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