Year | Value | 2017 | 2.985 | 2016 | 2.885 | 2015 | 2.908 | 2014 | 2.881 | 2013 | 2.83 | 2012 | 2.806 | 2011 | 2.767 | 2010 | 2.773 | 2009 | 2.709 | 2008 | 2.718 | 2007 | 2.694 | 2006 | 2.578 | 2005 | 2.56 | 2004 | 2.4568 | 2003 | 2.4011 | 2002 | 2.2696 | 2001 | 2.2172 | 2000 | 2.1509 | 1999 | 2.4878 | 1998 | 2.4354 | 1997 | 2.4 | 1996 | 2.319 | 1995 | 2.242 | 1994 | 2.164 | 1993 | 2.138 | 1992 | 2.079 | 1991 | 2.019 | 1990 | 2.009 | 1989 | 2 | 1988 | 1.9 | 1987 | 1.8 | 1986 | 1.9 | 1985 | 1.8 | 1984 | 1.7 | 1983 | 1.7 | 1982 | 1.7 | 1981 | 1.5 | 1980 | 1.7 | 1979 | 1.6 | 1978 | 1.5 | 1977 | 1.3 | 1976 | 1.3 | 1975 | 1.3 | 1974 | 1.2 | 1973 | 1.2 | 1972 | 1.2 | 1971 | 1.2 | 1970 | 1.1 | 1969 | 1.1 | 1968 | 1.1 | 1967 | 1 | 1966 | 1 | 1965 | 1 | 1964 | 1 | 1963 | 1 | 1962 | 1 | 1961 | 1 | 1960 | 1 |
|