Year | Value | 2021 | 1.64 | 2020 | 1.59 | 2019 | 1.57 | 2018 | 1.54 | 2017 | 1.52 | 2016 | 1.48 | 2015 | 1.4 | 2014 | 1.37 | 2013 | 1.34 | 2012 | 1.34 | 2011 | 1.45 | 2010 | 1.43 | 2009 | 1.44 | 2008 | 1.34 | 2007 | 1.27 | 2006 | 1.25 | 2005 | 1.27 | 2004 | 1.25 | 2003 | 1.2 | 2002 | 1.19 | 2001 | 1.2 | 2000 | 1.3 | 1999 | 1.33 | 1998 | 1.37 | 1997 | 1.43 | 1996 | 1.47 | 1995 | 1.52 | 1994 | 1.67 | 1993 | 1.87 | 1992 | 1.93 | 1991 | 2.05 | 1990 | 2.09 | 1989 | 2.07 | 1988 | 2.13 | 1987 | 2.14 | 1986 | 2.2 | 1985 | 2.26 | 1984 | 2.26 | 1983 | 2.28 | 1982 | 2.28 | 1981 | 2.29 | 1980 | 2.32 | 1979 | 2.45 | 1978 | 2.47 | 1977 | 2.49 | 1976 | 2.55 | 1975 | 2.55 | 1974 | 2.61 | 1973 | 2.56 | 1972 | 2.49 | 1971 | 2.43 | 1970 | 2.41 | 1969 | 2.43 | 1968 | 2.39 | 1967 | 2.48 | 1966 | 2.66 | 1965 | 2.78 | 1964 | 2.89 | 1963 | 2.92 | 1962 | 2.83 | 1961 | 2.96 | 1960 | 3.04 |
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