Year | Value | 2021 | 1.61 | 2020 | 1.58 | 2019 | 1.66 | 2018 | 1.67 | 2017 | 1.59 | 2016 | 1.6 | 2015 | 1.58 | 2014 | 1.54 | 2013 | 1.52 | 2012 | 1.56 | 2011 | 1.61 | 2010 | 1.72 | 2009 | 1.7 | 2008 | 1.72 | 2007 | 1.69 | 2006 | 1.58 | 2005 | 1.52 | 2004 | 1.47 | 2003 | 1.37 | 2002 | 1.36 | 2001 | 1.32 | 2000 | 1.36 | 1999 | 1.3 | 1998 | 1.28 | 1997 | 1.32 | 1996 | 1.37 | 1995 | 1.38 | 1994 | 1.42 | 1993 | 1.49 | 1992 | 1.71 | 1991 | 1.8 | 1990 | 2.05 | 1989 | 2.22 | 1988 | 2.27 | 1987 | 2.27 | 1986 | 2.18 | 1985 | 2.13 | 1984 | 2.17 | 1983 | 2.16 | 1982 | 2.07 | 1981 | 2.07 | 1980 | 2.02 | 1979 | 2 | 1978 | 2.02 | 1977 | 2.06 | 1976 | 2.07 | 1975 | 2.04 | 1974 | 2.07 | 1973 | 2.06 | 1972 | 2.13 | 1971 | 2.19 | 1970 | 2.17 | 1969 | 2.13 | 1968 | 2.03 | 1967 | 1.9 | 1966 | 1.87 | 1965 | 1.88 | 1964 | 1.94 | 1963 | 1.89 | 1962 | 1.95 | 1961 | 1.98 | 1960 | 1.98 |
|