Year | Value | 2021 | 1.72 | 2020 | 1.63 | 2019 | 1.71 | 2018 | 1.75 | 2017 | 1.77 | 2016 | 1.81 | 2015 | 1.85 | 2014 | 1.89 | 2013 | 1.93 | 2012 | 1.98 | 2011 | 2.03 | 2010 | 2.05 | 2009 | 2.06 | 2008 | 2.06 | 2007 | 2.01 | 2006 | 1.91 | 2005 | 1.86 | 2004 | 1.93 | 2003 | 1.96 | 2002 | 1.97 | 2001 | 1.94 | 2000 | 1.89 | 1999 | 1.9 | 1998 | 1.94 | 1997 | 1.93 | 1996 | 1.88 | 1995 | 1.84 | 1994 | 1.85 | 1993 | 1.9 | 1992 | 1.99 | 1991 | 2.08 | 1990 | 2.11 | 1989 | 2.08 | 1988 | 2.17 | 1987 | 2.32 | 1986 | 2.44 | 1985 | 2.48 | 1984 | 2.58 | 1983 | 2.74 | 1982 | 2.94 | 1981 | 3.05 | 1980 | 3.21 | 1979 | 3.21 | 1978 | 3.21 | 1977 | 3.24 | 1976 | 3.29 | 1975 | 3.37 | 1974 | 3.59 | 1973 | 3.71 | 1972 | 3.84 | 1971 | 3.93 | 1970 | 3.85 | 1969 | 3.83 | 1968 | 3.77 | 1967 | 3.84 | 1966 | 3.94 | 1965 | 4.04 | 1964 | 4.07 | 1963 | 4.01 | 1962 | 3.92 | 1961 | 3.78 | 1960 | 3.78 |
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